[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

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[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

[Vitaly Buka via cfe-commits]

https://github.com/vitalybuka closed 
https://github.com/llvm/llvm-project/pull/170822
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[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

[Vitaly Buka via cfe-commits]

https://github.com/vitalybuka auto_merge_enabled 
https://github.com/llvm/llvm-project/pull/170822
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[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

[Vitaly Buka via cfe-commits]

https://github.com/vitalybuka approved this pull request.

I suspect this new functionality is unnecessary micromanagement.
But I don't expect issues from having that.
So LGTM

https://github.com/llvm/llvm-project/pull/170822
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[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

[Florian Mayer via cfe-commits]

https://github.com/fmayer approved this pull request.


https://github.com/llvm/llvm-project/pull/170822
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[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

[via cfe-commits]

https://github.com/j39m updated https://github.com/llvm/llvm-project/pull/170822

>From 30462f19f6ba2bf53eb6440dff018c40282bf3fd Mon Sep 17 00:00:00 2001
From: Kalvin Lee 
Date: Fri, 5 Dec 2025 17:37:29 +0900
Subject: [PATCH 1/6] Add fine-grained `__has_feature()` cutout

This is a follow-up to pull 148323. It mints
`-fsanitize-ignore-for-ubsan-feature=...`, accepting a list of (UBSan)
sanitizers that should not cause
`__has_feature(undefined_behavior_sanitizer)` to evaluate true.
---
 .../clang/Basic/DiagnosticDriverKinds.td  |  1 +
 clang/include/clang/Basic/Features.def|  2 +-
 clang/include/clang/Basic/LangOptions.h   |  3 ++
 clang/include/clang/Driver/SanitizerArgs.h|  1 +
 clang/include/clang/Options/Options.td|  8 +
 clang/lib/Driver/SanitizerArgs.cpp| 29 ++
 clang/lib/Frontend/CompilerInvocation.cpp | 15 ++
 ...s_feature_undefined_behavior_sanitizer.cpp | 30 +++
 8 files changed, 88 insertions(+), 1 deletion(-)

diff --git a/clang/include/clang/Basic/DiagnosticDriverKinds.td 
b/clang/include/clang/Basic/DiagnosticDriverKinds.td
index aeffe96e806bd..9e5ca9f76397b 100644
--- a/clang/include/clang/Basic/DiagnosticDriverKinds.td
+++ b/clang/include/clang/Basic/DiagnosticDriverKinds.td
@@ -277,6 +277,7 @@ def err_drv_malformed_sanitizer_metadata_ignorelist : Error<
   "malformed sanitizer metadata ignorelist: '%0'">;
 def err_drv_unsupported_static_sanitizer_darwin : Error<
   "static %0 runtime is not supported on darwin">;
+def err_drv_not_a_ubsan_sanitizer : Error<"not a UBSan sanitizer: '%0'">;
 def err_drv_duplicate_config : Error<
   "no more than one option '--config' is allowed">;
 def err_drv_cannot_open_config_file : Error<
diff --git a/clang/include/clang/Basic/Features.def 
b/clang/include/clang/Basic/Features.def
index 0e91b42a132c1..52dd3a72392ee 100644
--- a/clang/include/clang/Basic/Features.def
+++ b/clang/include/clang/Basic/Features.def
@@ -53,7 +53,7 @@ FEATURE(memtag_globals,
 LangOpts.Sanitize.has(SanitizerKind::MemtagGlobals))
 FEATURE(xray_instrument, LangOpts.XRayInstrument)
 FEATURE(undefined_behavior_sanitizer,
-LangOpts.Sanitize.hasOneOf(SanitizerKind::Undefined))
+LangOpts.Sanitize.hasOneOf(SanitizerKind::Undefined & 
~LangOpts.UBSanFeatureSuppressedSanitize.Mask))
 FEATURE(undefined_behavior_sanitizer_finegrained_feature_checks, true)
 // These are all part of undefined_behavior_sanitizer:
 FEATURE(alignment_sanitizer,
diff --git a/clang/include/clang/Basic/LangOptions.h 
b/clang/include/clang/Basic/LangOptions.h
index 3f042f8ddb5a1..66fe01e877cb1 100644
--- a/clang/include/clang/Basic/LangOptions.h
+++ b/clang/include/clang/Basic/LangOptions.h
@@ -441,6 +441,9 @@ class LangOptions : public LangOptionsBase {
   SanitizerSet Sanitize;
   /// Is at least one coverage instrumentation type enabled.
   bool SanitizeCoverage = false;
+  /// Set of enabled (undefined behavior) sanitizers that do not cause
+  /// `__has_feature(undefined_behavior_sanitizer)` to evaluate true.
+  SanitizerSet UBSanFeatureSuppressedSanitize;
 
   /// Paths to files specifying which objects
   /// (files, functions, variables) should not be instrumented.
diff --git a/clang/include/clang/Driver/SanitizerArgs.h 
b/clang/include/clang/Driver/SanitizerArgs.h
index 84fb66e16bee3..aa8aa9be287c6 100644
--- a/clang/include/clang/Driver/SanitizerArgs.h
+++ b/clang/include/clang/Driver/SanitizerArgs.h
@@ -28,6 +28,7 @@ class SanitizerArgs {
   SanitizerSet MergeHandlers;
   SanitizerMaskCutoffs SkipHotCutoffs;
   SanitizerSet AnnotateDebugInfo;
+  SanitizerSet SuppressUBSanFeature;
 
   std::vector UserIgnorelistFiles;
   std::vector SystemIgnorelistFiles;
diff --git a/clang/include/clang/Options/Options.td 
b/clang/include/clang/Options/Options.td
index c6841937c8d39..84243ad80f2a1 100644
--- a/clang/include/clang/Options/Options.td
+++ b/clang/include/clang/Options/Options.td
@@ -2404,6 +2404,14 @@ def fsanitize_EQ : CommaJoined<["-"], "fsanitize=">, 
Group,
 "or suspicious behavior. See user manual for 
available checks">;
 def fno_sanitize_EQ : CommaJoined<["-"], "fno-sanitize=">, 
Group,
   Visibility<[ClangOption, CLOption]>;
+def fsanitize_ignore_for_ubsan_feature_EQ
+: CommaJoined<["-"], "fsanitize-ignore-for-ubsan-feature=">,
+  Group,
+  MetaVarName<"">,
+  HelpText<
+  "Prevents `__has_feature(undefined_behavior_sanitizer)` from "
+  "evaluating true for "
+  "these UBSan checks. See user manual for available UBSan checks">;
 
 def fsanitize_ignorelist_EQ : Joined<["-"], "fsanitize-ignorelist=">,
   Group, HelpText<"Path to ignorelist file for sanitizers">;
diff --git a/clang/lib/Driver/SanitizerArgs.cpp 
b/clang/lib/Driver/SanitizerArgs.cpp
index be068b2381d06..08db579626437 100644
--- a/clang/lib/Driver/SanitizerArgs.cpp
+++ b/clang/lib/Driver/SanitizerArgs.cpp
@@ -408,6 +408,8 @@ SanitizerArgs::Sani

[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

[via cfe-commits]

@@ -441,6 +441,9 @@ class LangOptions : public LangOptionsBase {
   SanitizerSet Sanitize;
   /// Is at least one coverage instrumentation type enabled.
   bool SanitizeCoverage = false;
+  /// Set of enabled (undefined behavior) sanitizers that do not cause

j39m wrote:

Pushing a fixup commit to incorporate...

https://github.com/llvm/llvm-project/pull/170822
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[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

[Florian Mayer via cfe-commits]

@@ -2421,6 +2404,14 @@ def fsanitize_EQ : CommaJoined<["-"], "fsanitize=">, 
Group,
 "or suspicious behavior. See user manual for 
available checks">;
 def fno_sanitize_EQ : CommaJoined<["-"], "fno-sanitize=">, 
Group,
   Visibility<[ClangOption, CLOption]>;
+def fsanitize_ignore_for_ubsan_feature_EQ
+: CommaJoined<["-"], "fsanitize-ignore-for-ubsan-feature=">,

fmayer wrote:

Because we want to be able to say which features do not count as UBSan enabled.

So we can say: "we do not consider array-bounds a sanitizer", and then when we 
_only_ enable that, the UBSan macro is not set.

https://github.com/llvm/llvm-project/pull/170822
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[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

[Vitaly Buka via cfe-commits]

@@ -2421,6 +2404,14 @@ def fsanitize_EQ : CommaJoined<["-"], "fsanitize=">, 
Group,
 "or suspicious behavior. See user manual for 
available checks">;
 def fno_sanitize_EQ : CommaJoined<["-"], "fno-sanitize=">, 
Group,
   Visibility<[ClangOption, CLOption]>;
+def fsanitize_ignore_for_ubsan_feature_EQ
+: CommaJoined<["-"], "fsanitize-ignore-for-ubsan-feature=">,

vitalybuka wrote:

I can see that #148323 breaks some pre-existing code.
If it's not large scale issue, it's probably does not worse of a new flag.

https://github.com/llvm/llvm-project/pull/170822
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[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

[Vitaly Buka via cfe-commits]

https://github.com/vitalybuka edited 
https://github.com/llvm/llvm-project/pull/170822
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[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

[Vitaly Buka via cfe-commits]

@@ -2421,6 +2404,14 @@ def fsanitize_EQ : CommaJoined<["-"], "fsanitize=">, 
Group,
 "or suspicious behavior. See user manual for 
available checks">;
 def fno_sanitize_EQ : CommaJoined<["-"], "fno-sanitize=">, 
Group,
   Visibility<[ClangOption, CLOption]>;
+def fsanitize_ignore_for_ubsan_feature_EQ
+: CommaJoined<["-"], "fsanitize-ignore-for-ubsan-feature=">,

vitalybuka wrote:

why do we need the flag?

https://github.com/llvm/llvm-project/pull/170822
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[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

[Florian Mayer via cfe-commits]

@@ -441,6 +441,9 @@ class LangOptions : public LangOptionsBase {
   SanitizerSet Sanitize;
   /// Is at least one coverage instrumentation type enabled.
   bool SanitizeCoverage = false;
+  /// Set of enabled (undefined behavior) sanitizers that do not cause

fmayer wrote:

I don't think this is correct? Isn't it "Set of  (UBSan) sanitizers that when 
enabled do not cause ..."?

https://github.com/llvm/llvm-project/pull/170822
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[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

[via cfe-commits]

@@ -277,6 +277,7 @@ def err_drv_malformed_sanitizer_metadata_ignorelist : Error<
   "malformed sanitizer metadata ignorelist: '%0'">;
 def err_drv_unsupported_static_sanitizer_darwin : Error<
   "static %0 runtime is not supported on darwin">;
+def err_drv_not_a_ubsan_sanitizer : Error<"not a UBSan sanitizer: '%0'">;

j39m wrote:

Thanks - fixed.

https://github.com/llvm/llvm-project/pull/170822
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[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

[via cfe-commits]

https://github.com/j39m updated https://github.com/llvm/llvm-project/pull/170822

>From 30462f19f6ba2bf53eb6440dff018c40282bf3fd Mon Sep 17 00:00:00 2001
From: Kalvin Lee 
Date: Fri, 5 Dec 2025 17:37:29 +0900
Subject: [PATCH 1/5] Add fine-grained `__has_feature()` cutout

This is a follow-up to pull 148323. It mints
`-fsanitize-ignore-for-ubsan-feature=...`, accepting a list of (UBSan)
sanitizers that should not cause
`__has_feature(undefined_behavior_sanitizer)` to evaluate true.
---
 .../clang/Basic/DiagnosticDriverKinds.td  |  1 +
 clang/include/clang/Basic/Features.def|  2 +-
 clang/include/clang/Basic/LangOptions.h   |  3 ++
 clang/include/clang/Driver/SanitizerArgs.h|  1 +
 clang/include/clang/Options/Options.td|  8 +
 clang/lib/Driver/SanitizerArgs.cpp| 29 ++
 clang/lib/Frontend/CompilerInvocation.cpp | 15 ++
 ...s_feature_undefined_behavior_sanitizer.cpp | 30 +++
 8 files changed, 88 insertions(+), 1 deletion(-)

diff --git a/clang/include/clang/Basic/DiagnosticDriverKinds.td 
b/clang/include/clang/Basic/DiagnosticDriverKinds.td
index aeffe96e806bd..9e5ca9f76397b 100644
--- a/clang/include/clang/Basic/DiagnosticDriverKinds.td
+++ b/clang/include/clang/Basic/DiagnosticDriverKinds.td
@@ -277,6 +277,7 @@ def err_drv_malformed_sanitizer_metadata_ignorelist : Error<
   "malformed sanitizer metadata ignorelist: '%0'">;
 def err_drv_unsupported_static_sanitizer_darwin : Error<
   "static %0 runtime is not supported on darwin">;
+def err_drv_not_a_ubsan_sanitizer : Error<"not a UBSan sanitizer: '%0'">;
 def err_drv_duplicate_config : Error<
   "no more than one option '--config' is allowed">;
 def err_drv_cannot_open_config_file : Error<
diff --git a/clang/include/clang/Basic/Features.def 
b/clang/include/clang/Basic/Features.def
index 0e91b42a132c1..52dd3a72392ee 100644
--- a/clang/include/clang/Basic/Features.def
+++ b/clang/include/clang/Basic/Features.def
@@ -53,7 +53,7 @@ FEATURE(memtag_globals,
 LangOpts.Sanitize.has(SanitizerKind::MemtagGlobals))
 FEATURE(xray_instrument, LangOpts.XRayInstrument)
 FEATURE(undefined_behavior_sanitizer,
-LangOpts.Sanitize.hasOneOf(SanitizerKind::Undefined))
+LangOpts.Sanitize.hasOneOf(SanitizerKind::Undefined & 
~LangOpts.UBSanFeatureSuppressedSanitize.Mask))
 FEATURE(undefined_behavior_sanitizer_finegrained_feature_checks, true)
 // These are all part of undefined_behavior_sanitizer:
 FEATURE(alignment_sanitizer,
diff --git a/clang/include/clang/Basic/LangOptions.h 
b/clang/include/clang/Basic/LangOptions.h
index 3f042f8ddb5a1..66fe01e877cb1 100644
--- a/clang/include/clang/Basic/LangOptions.h
+++ b/clang/include/clang/Basic/LangOptions.h
@@ -441,6 +441,9 @@ class LangOptions : public LangOptionsBase {
   SanitizerSet Sanitize;
   /// Is at least one coverage instrumentation type enabled.
   bool SanitizeCoverage = false;
+  /// Set of enabled (undefined behavior) sanitizers that do not cause
+  /// `__has_feature(undefined_behavior_sanitizer)` to evaluate true.
+  SanitizerSet UBSanFeatureSuppressedSanitize;
 
   /// Paths to files specifying which objects
   /// (files, functions, variables) should not be instrumented.
diff --git a/clang/include/clang/Driver/SanitizerArgs.h 
b/clang/include/clang/Driver/SanitizerArgs.h
index 84fb66e16bee3..aa8aa9be287c6 100644
--- a/clang/include/clang/Driver/SanitizerArgs.h
+++ b/clang/include/clang/Driver/SanitizerArgs.h
@@ -28,6 +28,7 @@ class SanitizerArgs {
   SanitizerSet MergeHandlers;
   SanitizerMaskCutoffs SkipHotCutoffs;
   SanitizerSet AnnotateDebugInfo;
+  SanitizerSet SuppressUBSanFeature;
 
   std::vector UserIgnorelistFiles;
   std::vector SystemIgnorelistFiles;
diff --git a/clang/include/clang/Options/Options.td 
b/clang/include/clang/Options/Options.td
index c6841937c8d39..84243ad80f2a1 100644
--- a/clang/include/clang/Options/Options.td
+++ b/clang/include/clang/Options/Options.td
@@ -2404,6 +2404,14 @@ def fsanitize_EQ : CommaJoined<["-"], "fsanitize=">, 
Group,
 "or suspicious behavior. See user manual for 
available checks">;
 def fno_sanitize_EQ : CommaJoined<["-"], "fno-sanitize=">, 
Group,
   Visibility<[ClangOption, CLOption]>;
+def fsanitize_ignore_for_ubsan_feature_EQ
+: CommaJoined<["-"], "fsanitize-ignore-for-ubsan-feature=">,
+  Group,
+  MetaVarName<"">,
+  HelpText<
+  "Prevents `__has_feature(undefined_behavior_sanitizer)` from "
+  "evaluating true for "
+  "these UBSan checks. See user manual for available UBSan checks">;
 
 def fsanitize_ignorelist_EQ : Joined<["-"], "fsanitize-ignorelist=">,
   Group, HelpText<"Path to ignorelist file for sanitizers">;
diff --git a/clang/lib/Driver/SanitizerArgs.cpp 
b/clang/lib/Driver/SanitizerArgs.cpp
index be068b2381d06..08db579626437 100644
--- a/clang/lib/Driver/SanitizerArgs.cpp
+++ b/clang/lib/Driver/SanitizerArgs.cpp
@@ -408,6 +408,8 @@ SanitizerArgs::Sani

[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

[via cfe-commits]

https://github.com/j39m updated https://github.com/llvm/llvm-project/pull/170822

>From 30462f19f6ba2bf53eb6440dff018c40282bf3fd Mon Sep 17 00:00:00 2001
From: Kalvin Lee 
Date: Fri, 5 Dec 2025 17:37:29 +0900
Subject: [PATCH 1/4] Add fine-grained `__has_feature()` cutout

This is a follow-up to pull 148323. It mints
`-fsanitize-ignore-for-ubsan-feature=...`, accepting a list of (UBSan)
sanitizers that should not cause
`__has_feature(undefined_behavior_sanitizer)` to evaluate true.
---
 .../clang/Basic/DiagnosticDriverKinds.td  |  1 +
 clang/include/clang/Basic/Features.def|  2 +-
 clang/include/clang/Basic/LangOptions.h   |  3 ++
 clang/include/clang/Driver/SanitizerArgs.h|  1 +
 clang/include/clang/Options/Options.td|  8 +
 clang/lib/Driver/SanitizerArgs.cpp| 29 ++
 clang/lib/Frontend/CompilerInvocation.cpp | 15 ++
 ...s_feature_undefined_behavior_sanitizer.cpp | 30 +++
 8 files changed, 88 insertions(+), 1 deletion(-)

diff --git a/clang/include/clang/Basic/DiagnosticDriverKinds.td 
b/clang/include/clang/Basic/DiagnosticDriverKinds.td
index aeffe96e806bd..9e5ca9f76397b 100644
--- a/clang/include/clang/Basic/DiagnosticDriverKinds.td
+++ b/clang/include/clang/Basic/DiagnosticDriverKinds.td
@@ -277,6 +277,7 @@ def err_drv_malformed_sanitizer_metadata_ignorelist : Error<
   "malformed sanitizer metadata ignorelist: '%0'">;
 def err_drv_unsupported_static_sanitizer_darwin : Error<
   "static %0 runtime is not supported on darwin">;
+def err_drv_not_a_ubsan_sanitizer : Error<"not a UBSan sanitizer: '%0'">;
 def err_drv_duplicate_config : Error<
   "no more than one option '--config' is allowed">;
 def err_drv_cannot_open_config_file : Error<
diff --git a/clang/include/clang/Basic/Features.def 
b/clang/include/clang/Basic/Features.def
index 0e91b42a132c1..52dd3a72392ee 100644
--- a/clang/include/clang/Basic/Features.def
+++ b/clang/include/clang/Basic/Features.def
@@ -53,7 +53,7 @@ FEATURE(memtag_globals,
 LangOpts.Sanitize.has(SanitizerKind::MemtagGlobals))
 FEATURE(xray_instrument, LangOpts.XRayInstrument)
 FEATURE(undefined_behavior_sanitizer,
-LangOpts.Sanitize.hasOneOf(SanitizerKind::Undefined))
+LangOpts.Sanitize.hasOneOf(SanitizerKind::Undefined & 
~LangOpts.UBSanFeatureSuppressedSanitize.Mask))
 FEATURE(undefined_behavior_sanitizer_finegrained_feature_checks, true)
 // These are all part of undefined_behavior_sanitizer:
 FEATURE(alignment_sanitizer,
diff --git a/clang/include/clang/Basic/LangOptions.h 
b/clang/include/clang/Basic/LangOptions.h
index 3f042f8ddb5a1..66fe01e877cb1 100644
--- a/clang/include/clang/Basic/LangOptions.h
+++ b/clang/include/clang/Basic/LangOptions.h
@@ -441,6 +441,9 @@ class LangOptions : public LangOptionsBase {
   SanitizerSet Sanitize;
   /// Is at least one coverage instrumentation type enabled.
   bool SanitizeCoverage = false;
+  /// Set of enabled (undefined behavior) sanitizers that do not cause
+  /// `__has_feature(undefined_behavior_sanitizer)` to evaluate true.
+  SanitizerSet UBSanFeatureSuppressedSanitize;
 
   /// Paths to files specifying which objects
   /// (files, functions, variables) should not be instrumented.
diff --git a/clang/include/clang/Driver/SanitizerArgs.h 
b/clang/include/clang/Driver/SanitizerArgs.h
index 84fb66e16bee3..aa8aa9be287c6 100644
--- a/clang/include/clang/Driver/SanitizerArgs.h
+++ b/clang/include/clang/Driver/SanitizerArgs.h
@@ -28,6 +28,7 @@ class SanitizerArgs {
   SanitizerSet MergeHandlers;
   SanitizerMaskCutoffs SkipHotCutoffs;
   SanitizerSet AnnotateDebugInfo;
+  SanitizerSet SuppressUBSanFeature;
 
   std::vector UserIgnorelistFiles;
   std::vector SystemIgnorelistFiles;
diff --git a/clang/include/clang/Options/Options.td 
b/clang/include/clang/Options/Options.td
index c6841937c8d39..84243ad80f2a1 100644
--- a/clang/include/clang/Options/Options.td
+++ b/clang/include/clang/Options/Options.td
@@ -2404,6 +2404,14 @@ def fsanitize_EQ : CommaJoined<["-"], "fsanitize=">, 
Group,
 "or suspicious behavior. See user manual for 
available checks">;
 def fno_sanitize_EQ : CommaJoined<["-"], "fno-sanitize=">, 
Group,
   Visibility<[ClangOption, CLOption]>;
+def fsanitize_ignore_for_ubsan_feature_EQ
+: CommaJoined<["-"], "fsanitize-ignore-for-ubsan-feature=">,
+  Group,
+  MetaVarName<"">,
+  HelpText<
+  "Prevents `__has_feature(undefined_behavior_sanitizer)` from "
+  "evaluating true for "
+  "these UBSan checks. See user manual for available UBSan checks">;
 
 def fsanitize_ignorelist_EQ : Joined<["-"], "fsanitize-ignorelist=">,
   Group, HelpText<"Path to ignorelist file for sanitizers">;
diff --git a/clang/lib/Driver/SanitizerArgs.cpp 
b/clang/lib/Driver/SanitizerArgs.cpp
index be068b2381d06..08db579626437 100644
--- a/clang/lib/Driver/SanitizerArgs.cpp
+++ b/clang/lib/Driver/SanitizerArgs.cpp
@@ -408,6 +408,8 @@ SanitizerArgs::Sani

[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

[via cfe-commits]

j39m wrote:

I've been waiting on the `build and test {linux,windows}` steps for a few days 
now. Is there something I need to do to make them resolve?

I will still need a hint on what build target to use to repro the failure in my 
tree.

https://github.com/llvm/llvm-project/pull/170822
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[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

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j39m wrote:

I'm unable to reproduce the test failure in my checkout. I tried mimicking a 
subset of `monolithic-linux.sh`, but neither of `check-clang` or 
`check-clang-tools` produces any failures that I can see.

https://github.com/llvm/llvm-project/pull/170822
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[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

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https://github.com/j39m updated https://github.com/llvm/llvm-project/pull/170822

>From 30462f19f6ba2bf53eb6440dff018c40282bf3fd Mon Sep 17 00:00:00 2001
From: Kalvin Lee 
Date: Fri, 5 Dec 2025 17:37:29 +0900
Subject: [PATCH 1/3] Add fine-grained `__has_feature()` cutout

This is a follow-up to pull 148323. It mints
`-fsanitize-ignore-for-ubsan-feature=...`, accepting a list of (UBSan)
sanitizers that should not cause
`__has_feature(undefined_behavior_sanitizer)` to evaluate true.
---
 .../clang/Basic/DiagnosticDriverKinds.td  |  1 +
 clang/include/clang/Basic/Features.def|  2 +-
 clang/include/clang/Basic/LangOptions.h   |  3 ++
 clang/include/clang/Driver/SanitizerArgs.h|  1 +
 clang/include/clang/Options/Options.td|  8 +
 clang/lib/Driver/SanitizerArgs.cpp| 29 ++
 clang/lib/Frontend/CompilerInvocation.cpp | 15 ++
 ...s_feature_undefined_behavior_sanitizer.cpp | 30 +++
 8 files changed, 88 insertions(+), 1 deletion(-)

diff --git a/clang/include/clang/Basic/DiagnosticDriverKinds.td 
b/clang/include/clang/Basic/DiagnosticDriverKinds.td
index aeffe96e806bd..9e5ca9f76397b 100644
--- a/clang/include/clang/Basic/DiagnosticDriverKinds.td
+++ b/clang/include/clang/Basic/DiagnosticDriverKinds.td
@@ -277,6 +277,7 @@ def err_drv_malformed_sanitizer_metadata_ignorelist : Error<
   "malformed sanitizer metadata ignorelist: '%0'">;
 def err_drv_unsupported_static_sanitizer_darwin : Error<
   "static %0 runtime is not supported on darwin">;
+def err_drv_not_a_ubsan_sanitizer : Error<"not a UBSan sanitizer: '%0'">;
 def err_drv_duplicate_config : Error<
   "no more than one option '--config' is allowed">;
 def err_drv_cannot_open_config_file : Error<
diff --git a/clang/include/clang/Basic/Features.def 
b/clang/include/clang/Basic/Features.def
index 0e91b42a132c1..52dd3a72392ee 100644
--- a/clang/include/clang/Basic/Features.def
+++ b/clang/include/clang/Basic/Features.def
@@ -53,7 +53,7 @@ FEATURE(memtag_globals,
 LangOpts.Sanitize.has(SanitizerKind::MemtagGlobals))
 FEATURE(xray_instrument, LangOpts.XRayInstrument)
 FEATURE(undefined_behavior_sanitizer,
-LangOpts.Sanitize.hasOneOf(SanitizerKind::Undefined))
+LangOpts.Sanitize.hasOneOf(SanitizerKind::Undefined & 
~LangOpts.UBSanFeatureSuppressedSanitize.Mask))
 FEATURE(undefined_behavior_sanitizer_finegrained_feature_checks, true)
 // These are all part of undefined_behavior_sanitizer:
 FEATURE(alignment_sanitizer,
diff --git a/clang/include/clang/Basic/LangOptions.h 
b/clang/include/clang/Basic/LangOptions.h
index 3f042f8ddb5a1..66fe01e877cb1 100644
--- a/clang/include/clang/Basic/LangOptions.h
+++ b/clang/include/clang/Basic/LangOptions.h
@@ -441,6 +441,9 @@ class LangOptions : public LangOptionsBase {
   SanitizerSet Sanitize;
   /// Is at least one coverage instrumentation type enabled.
   bool SanitizeCoverage = false;
+  /// Set of enabled (undefined behavior) sanitizers that do not cause
+  /// `__has_feature(undefined_behavior_sanitizer)` to evaluate true.
+  SanitizerSet UBSanFeatureSuppressedSanitize;
 
   /// Paths to files specifying which objects
   /// (files, functions, variables) should not be instrumented.
diff --git a/clang/include/clang/Driver/SanitizerArgs.h 
b/clang/include/clang/Driver/SanitizerArgs.h
index 84fb66e16bee3..aa8aa9be287c6 100644
--- a/clang/include/clang/Driver/SanitizerArgs.h
+++ b/clang/include/clang/Driver/SanitizerArgs.h
@@ -28,6 +28,7 @@ class SanitizerArgs {
   SanitizerSet MergeHandlers;
   SanitizerMaskCutoffs SkipHotCutoffs;
   SanitizerSet AnnotateDebugInfo;
+  SanitizerSet SuppressUBSanFeature;
 
   std::vector UserIgnorelistFiles;
   std::vector SystemIgnorelistFiles;
diff --git a/clang/include/clang/Options/Options.td 
b/clang/include/clang/Options/Options.td
index c6841937c8d39..84243ad80f2a1 100644
--- a/clang/include/clang/Options/Options.td
+++ b/clang/include/clang/Options/Options.td
@@ -2404,6 +2404,14 @@ def fsanitize_EQ : CommaJoined<["-"], "fsanitize=">, 
Group,
 "or suspicious behavior. See user manual for 
available checks">;
 def fno_sanitize_EQ : CommaJoined<["-"], "fno-sanitize=">, 
Group,
   Visibility<[ClangOption, CLOption]>;
+def fsanitize_ignore_for_ubsan_feature_EQ
+: CommaJoined<["-"], "fsanitize-ignore-for-ubsan-feature=">,
+  Group,
+  MetaVarName<"">,
+  HelpText<
+  "Prevents `__has_feature(undefined_behavior_sanitizer)` from "
+  "evaluating true for "
+  "these UBSan checks. See user manual for available UBSan checks">;
 
 def fsanitize_ignorelist_EQ : Joined<["-"], "fsanitize-ignorelist=">,
   Group, HelpText<"Path to ignorelist file for sanitizers">;
diff --git a/clang/lib/Driver/SanitizerArgs.cpp 
b/clang/lib/Driver/SanitizerArgs.cpp
index be068b2381d06..08db579626437 100644
--- a/clang/lib/Driver/SanitizerArgs.cpp
+++ b/clang/lib/Driver/SanitizerArgs.cpp
@@ -408,6 +408,8 @@ SanitizerArgs::Sani

[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

[Florian Mayer via cfe-commits]

fmayer wrote:

Please fix test failure

https://github.com/llvm/llvm-project/pull/170822
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[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

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github-actions[bot] wrote:


# :window: Windows x64 Test Results

* 51416 tests passed
* 852 tests skipped
* 1 test failed

## Failed Tests
(click on a test name to see its output)

### Clang

Clang.Lexer/has_feature_undefined_behavior_sanitizer.cpp

```
Exit Code: 2

Command Output (stdout):
--
# RUN: at line 1
c:\_work\llvm-project\llvm-project\build\bin\clang.exe -E -target 
x86_64-unknown-linux-gnu -fsanitize=undefined 
C:\_work\llvm-project\llvm-project\clang\test\Lexer\has_feature_undefined_behavior_sanitizer.cpp
 -o - | c:\_work\llvm-project\llvm-project\build\bin\filecheck.exe 
--check-prefix=CHECK-UBSAN 
C:\_work\llvm-project\llvm-project\clang\test\Lexer\has_feature_undefined_behavior_sanitizer.cpp
# executed command: 'c:\_work\llvm-project\llvm-project\build\bin\clang.exe' -E 
-target x86_64-unknown-linux-gnu -fsanitize=undefined 
'C:\_work\llvm-project\llvm-project\clang\test\Lexer\has_feature_undefined_behavior_sanitizer.cpp'
 -o -
# note: command had no output on stdout or stderr
# executed command: 
'c:\_work\llvm-project\llvm-project\build\bin\filecheck.exe' 
--check-prefix=CHECK-UBSAN 
'C:\_work\llvm-project\llvm-project\clang\test\Lexer\has_feature_undefined_behavior_sanitizer.cpp'
# note: command had no output on stdout or stderr
# RUN: at line 2
c:\_work\llvm-project\llvm-project\build\bin\clang.exe -E -target 
x86_64-unknown-linux-gnu -fsanitize=alignment 
C:\_work\llvm-project\llvm-project\clang\test\Lexer\has_feature_undefined_behavior_sanitizer.cpp
 -o - | c:\_work\llvm-project\llvm-project\build\bin\filecheck.exe 
--check-prefixes=CHECK-UBSAN,CHECK-ALIGNMENT 
C:\_work\llvm-project\llvm-project\clang\test\Lexer\has_feature_undefined_behavior_sanitizer.cpp
# executed command: 'c:\_work\llvm-project\llvm-project\build\bin\clang.exe' -E 
-target x86_64-unknown-linux-gnu -fsanitize=alignment 
'C:\_work\llvm-project\llvm-project\clang\test\Lexer\has_feature_undefined_behavior_sanitizer.cpp'
 -o -
# note: command had no output on stdout or stderr
# executed command: 
'c:\_work\llvm-project\llvm-project\build\bin\filecheck.exe' 
--check-prefixes=CHECK-UBSAN,CHECK-ALIGNMENT 
'C:\_work\llvm-project\llvm-project\clang\test\Lexer\has_feature_undefined_behavior_sanitizer.cpp'
# note: command had no output on stdout or stderr
# RUN: at line 3
c:\_work\llvm-project\llvm-project\build\bin\clang.exe -E -target 
x86_64-unknown-linux-gnu -fsanitize=bool 
C:\_work\llvm-project\llvm-project\clang\test\Lexer\has_feature_undefined_behavior_sanitizer.cpp
 -o - | c:\_work\llvm-project\llvm-project\build\bin\filecheck.exe 
--check-prefixes=CHECK-UBSAN,CHECK-BOOL 
C:\_work\llvm-project\llvm-project\clang\test\Lexer\has_feature_undefined_behavior_sanitizer.cpp
# executed command: 'c:\_work\llvm-project\llvm-project\build\bin\clang.exe' -E 
-target x86_64-unknown-linux-gnu -fsanitize=bool 
'C:\_work\llvm-project\llvm-project\clang\test\Lexer\has_feature_undefined_behavior_sanitizer.cpp'
 -o -
# note: command had no output on stdout or stderr
# executed command: 
'c:\_work\llvm-project\llvm-project\build\bin\filecheck.exe' 
--check-prefixes=CHECK-UBSAN,CHECK-BOOL 
'C:\_work\llvm-project\llvm-project\clang\test\Lexer\has_feature_undefined_behavior_sanitizer.cpp'
# note: command had no output on stdout or stderr
# RUN: at line 4
c:\_work\llvm-project\llvm-project\build\bin\clang.exe -E -target 
x86_64-unknown-linux-gnu -fsanitize=builtin 
C:\_work\llvm-project\llvm-project\clang\test\Lexer\has_feature_undefined_behavior_sanitizer.cpp
 -o - | c:\_work\llvm-project\llvm-project\build\bin\filecheck.exe 
--check-prefixes=CHECK-UBSAN,CHECK-BUILTIN 
C:\_work\llvm-project\llvm-project\clang\test\Lexer\has_feature_undefined_behavior_sanitizer.cpp
# executed command: 'c:\_work\llvm-project\llvm-project\build\bin\clang.exe' -E 
-target x86_64-unknown-linux-gnu -fsanitize=builtin 
'C:\_work\llvm-project\llvm-project\clang\test\Lexer\has_feature_undefined_behavior_sanitizer.cpp'
 -o -
# note: command had no output on stdout or stderr
# executed command: 
'c:\_work\llvm-project\llvm-project\build\bin\filecheck.exe' 
--check-prefixes=CHECK-UBSAN,CHECK-BUILTIN 
'C:\_work\llvm-project\llvm-project\clang\test\Lexer\has_feature_undefined_behavior_sanitizer.cpp'
# note: command had no output on stdout or stderr
# RUN: at line 5
c:\_work\llvm-project\llvm-project\build\bin\clang.exe -E -target 
x86_64-unknown-linux-gnu -fsanitize=array-bounds 
C:\_work\llvm-project\llvm-project\clang\test\Lexer\has_feature_undefined_behavior_sanitizer.cpp
 -o - | c:\_work\llvm-project\llvm-project\build\bin\filecheck.exe 
--check-prefixes=CHECK-UBSAN,CHECK-ARRAY-BOUNDS 
C:\_work\llvm-project\llvm-project\clang\test\Lexer\has_feature_undefined_behavior_sanitizer.cpp
# executed command: 'c:\_work\llvm-project\llvm-project\build\bin\clang.exe' -E 
-target x86_64-unknown-linux-gnu -fsanitize=array-bounds 
'C:\_work\llvm-project\llvm-project\clang\test\Lexer\has_feature_undefined_behavior_sanitizer.cpp'
 -o -
# note: command had no output on stdout or s

[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

[via cfe-commits]

@@ -736,6 +743,22 @@ SanitizerArgs::SanitizerArgs(const ToolChain &TC,
   // -f(-no)sanitize=leak should change whether leak detection is enabled by
   // default in ASan?
 
+  // Error if a non-UBSan sanitizer is passed to
+  // `-fsanitize-ignore-for-ubsan-feature=`.
+  //
+  // `shift` is a `SANITIZER_GROUP()`, and so is expanded into its constituents
+  // by `expandSanitizerGroups()` above, though the physical bit is not 
included
+  // in `SanitizerKind::Undefined`.
+  const SanitizerMask not_ubsan_mask =
+  IgnoreForUbsanFeature &
+  ~(SanitizerKind::Undefined | SanitizerKind::ShiftGroup);

j39m wrote:

Understood --- removed all this in the follow-up.

https://github.com/llvm/llvm-project/pull/170822
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[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

[via cfe-commits]

@@ -3973,6 +3980,10 @@ bool CompilerInvocation::ParseLangArgs(LangOptions 
&Opts, ArgList &Args,
 Opts.PIE = Args.hasArg(OPT_pic_is_pie);
 parseSanitizerKinds("-fsanitize=", Args.getAllArgValues(OPT_fsanitize_EQ),
 Diags, Opts.Sanitize);
+parseSanitizerKinds(
+"-fsanitize-ignore-for-ubsan-feature=",
+Args.getAllArgValues(OPT_fsanitize_ignore_for_ubsan_feature_EQ), Diags,
+Opts.UBSanFeatureSuppressedSanitize);

j39m wrote:

Thanks --- fixed in a follow-up.

https://github.com/llvm/llvm-project/pull/170822
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[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

[Florian Mayer via cfe-commits]

@@ -736,6 +743,22 @@ SanitizerArgs::SanitizerArgs(const ToolChain &TC,
   // -f(-no)sanitize=leak should change whether leak detection is enabled by
   // default in ASan?
 
+  // Error if a non-UBSan sanitizer is passed to
+  // `-fsanitize-ignore-for-ubsan-feature=`.
+  //
+  // `shift` is a `SANITIZER_GROUP()`, and so is expanded into its constituents
+  // by `expandSanitizerGroups()` above, though the physical bit is not 
included
+  // in `SanitizerKind::Undefined`.
+  const SanitizerMask not_ubsan_mask =
+  IgnoreForUbsanFeature &
+  ~(SanitizerKind::Undefined | SanitizerKind::ShiftGroup);

fmayer wrote:

hmmm. not sure this gymnastics are worth if for the warning

https://github.com/llvm/llvm-project/pull/170822
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[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

[Florian Mayer via cfe-commits]

@@ -3973,6 +3980,10 @@ bool CompilerInvocation::ParseLangArgs(LangOptions 
&Opts, ArgList &Args,
 Opts.PIE = Args.hasArg(OPT_pic_is_pie);
 parseSanitizerKinds("-fsanitize=", Args.getAllArgValues(OPT_fsanitize_EQ),
 Diags, Opts.Sanitize);
+parseSanitizerKinds(
+"-fsanitize-ignore-for-ubsan-feature=",
+Args.getAllArgValues(OPT_fsanitize_ignore_for_ubsan_feature_EQ), Diags,
+Opts.UBSanFeatureSuppressedSanitize);

fmayer wrote:

I would use consistent terminology regarding `ignore` or `suppress` for the 
flag and the opt

https://github.com/llvm/llvm-project/pull/170822
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[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

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j39m wrote:

CC @fmayer (for general observation from afar)

https://github.com/llvm/llvm-project/pull/170822
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[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

[via cfe-commits]

llvmbot wrote:




@llvm/pr-subscribers-clang

Author: Kalvin (j39m)


Changes

This is a follow-up to pull 148323. It mints
`-fsanitize-ignore-for-ubsan-feature=...`, accepting a list of (UBSan) 
sanitizers that should not cause
`__has_feature(undefined_behavior_sanitizer)` to evaluate true.

---
Full diff: https://github.com/llvm/llvm-project/pull/170822.diff


8 Files Affected:

- (modified) clang/include/clang/Basic/DiagnosticDriverKinds.td (+1) 
- (modified) clang/include/clang/Basic/Features.def (+1-1) 
- (modified) clang/include/clang/Basic/LangOptions.h (+3) 
- (modified) clang/include/clang/Driver/SanitizerArgs.h (+1) 
- (modified) clang/include/clang/Options/Options.td (+8) 
- (modified) clang/lib/Driver/SanitizerArgs.cpp (+29) 
- (modified) clang/lib/Frontend/CompilerInvocation.cpp (+15) 
- (modified) clang/test/Lexer/has_feature_undefined_behavior_sanitizer.cpp 
(+30) 


``diff
diff --git a/clang/include/clang/Basic/DiagnosticDriverKinds.td 
b/clang/include/clang/Basic/DiagnosticDriverKinds.td
index aeffe96e806bd..9e5ca9f76397b 100644
--- a/clang/include/clang/Basic/DiagnosticDriverKinds.td
+++ b/clang/include/clang/Basic/DiagnosticDriverKinds.td
@@ -277,6 +277,7 @@ def err_drv_malformed_sanitizer_metadata_ignorelist : Error<
   "malformed sanitizer metadata ignorelist: '%0'">;
 def err_drv_unsupported_static_sanitizer_darwin : Error<
   "static %0 runtime is not supported on darwin">;
+def err_drv_not_a_ubsan_sanitizer : Error<"not a UBSan sanitizer: '%0'">;
 def err_drv_duplicate_config : Error<
   "no more than one option '--config' is allowed">;
 def err_drv_cannot_open_config_file : Error<
diff --git a/clang/include/clang/Basic/Features.def 
b/clang/include/clang/Basic/Features.def
index 0e91b42a132c1..52dd3a72392ee 100644
--- a/clang/include/clang/Basic/Features.def
+++ b/clang/include/clang/Basic/Features.def
@@ -53,7 +53,7 @@ FEATURE(memtag_globals,
 LangOpts.Sanitize.has(SanitizerKind::MemtagGlobals))
 FEATURE(xray_instrument, LangOpts.XRayInstrument)
 FEATURE(undefined_behavior_sanitizer,
-LangOpts.Sanitize.hasOneOf(SanitizerKind::Undefined))
+LangOpts.Sanitize.hasOneOf(SanitizerKind::Undefined & 
~LangOpts.UBSanFeatureSuppressedSanitize.Mask))
 FEATURE(undefined_behavior_sanitizer_finegrained_feature_checks, true)
 // These are all part of undefined_behavior_sanitizer:
 FEATURE(alignment_sanitizer,
diff --git a/clang/include/clang/Basic/LangOptions.h 
b/clang/include/clang/Basic/LangOptions.h
index 3f042f8ddb5a1..66fe01e877cb1 100644
--- a/clang/include/clang/Basic/LangOptions.h
+++ b/clang/include/clang/Basic/LangOptions.h
@@ -441,6 +441,9 @@ class LangOptions : public LangOptionsBase {
   SanitizerSet Sanitize;
   /// Is at least one coverage instrumentation type enabled.
   bool SanitizeCoverage = false;
+  /// Set of enabled (undefined behavior) sanitizers that do not cause
+  /// `__has_feature(undefined_behavior_sanitizer)` to evaluate true.
+  SanitizerSet UBSanFeatureSuppressedSanitize;
 
   /// Paths to files specifying which objects
   /// (files, functions, variables) should not be instrumented.
diff --git a/clang/include/clang/Driver/SanitizerArgs.h 
b/clang/include/clang/Driver/SanitizerArgs.h
index 84fb66e16bee3..aa8aa9be287c6 100644
--- a/clang/include/clang/Driver/SanitizerArgs.h
+++ b/clang/include/clang/Driver/SanitizerArgs.h
@@ -28,6 +28,7 @@ class SanitizerArgs {
   SanitizerSet MergeHandlers;
   SanitizerMaskCutoffs SkipHotCutoffs;
   SanitizerSet AnnotateDebugInfo;
+  SanitizerSet SuppressUBSanFeature;
 
   std::vector UserIgnorelistFiles;
   std::vector SystemIgnorelistFiles;
diff --git a/clang/include/clang/Options/Options.td 
b/clang/include/clang/Options/Options.td
index c6841937c8d39..84243ad80f2a1 100644
--- a/clang/include/clang/Options/Options.td
+++ b/clang/include/clang/Options/Options.td
@@ -2404,6 +2404,14 @@ def fsanitize_EQ : CommaJoined<["-"], "fsanitize=">, 
Group,
 "or suspicious behavior. See user manual for 
available checks">;
 def fno_sanitize_EQ : CommaJoined<["-"], "fno-sanitize=">, 
Group,
   Visibility<[ClangOption, CLOption]>;
+def fsanitize_ignore_for_ubsan_feature_EQ
+: CommaJoined<["-"], "fsanitize-ignore-for-ubsan-feature=">,
+  Group,
+  MetaVarName<"">,
+  HelpText<
+  "Prevents `__has_feature(undefined_behavior_sanitizer)` from "
+  "evaluating true for "
+  "these UBSan checks. See user manual for available UBSan checks">;
 
 def fsanitize_ignorelist_EQ : Joined<["-"], "fsanitize-ignorelist=">,
   Group, HelpText<"Path to ignorelist file for sanitizers">;
diff --git a/clang/lib/Driver/SanitizerArgs.cpp 
b/clang/lib/Driver/SanitizerArgs.cpp
index be068b2381d06..08db579626437 100644
--- a/clang/lib/Driver/SanitizerArgs.cpp
+++ b/clang/lib/Driver/SanitizerArgs.cpp
@@ -408,6 +408,8 @@ SanitizerArgs::SanitizerArgs(const ToolChain &TC,
 // unused-argument diagnostics.
   SanitizerMask

[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

[via cfe-commits]

llvmbot wrote:




@llvm/pr-subscribers-clang-driver

Author: Kalvin (j39m)


Changes

This is a follow-up to pull 148323. It mints
`-fsanitize-ignore-for-ubsan-feature=...`, accepting a list of (UBSan) 
sanitizers that should not cause
`__has_feature(undefined_behavior_sanitizer)` to evaluate true.

---
Full diff: https://github.com/llvm/llvm-project/pull/170822.diff


8 Files Affected:

- (modified) clang/include/clang/Basic/DiagnosticDriverKinds.td (+1) 
- (modified) clang/include/clang/Basic/Features.def (+1-1) 
- (modified) clang/include/clang/Basic/LangOptions.h (+3) 
- (modified) clang/include/clang/Driver/SanitizerArgs.h (+1) 
- (modified) clang/include/clang/Options/Options.td (+8) 
- (modified) clang/lib/Driver/SanitizerArgs.cpp (+29) 
- (modified) clang/lib/Frontend/CompilerInvocation.cpp (+15) 
- (modified) clang/test/Lexer/has_feature_undefined_behavior_sanitizer.cpp 
(+30) 


``diff
diff --git a/clang/include/clang/Basic/DiagnosticDriverKinds.td 
b/clang/include/clang/Basic/DiagnosticDriverKinds.td
index aeffe96e806bd..9e5ca9f76397b 100644
--- a/clang/include/clang/Basic/DiagnosticDriverKinds.td
+++ b/clang/include/clang/Basic/DiagnosticDriverKinds.td
@@ -277,6 +277,7 @@ def err_drv_malformed_sanitizer_metadata_ignorelist : Error<
   "malformed sanitizer metadata ignorelist: '%0'">;
 def err_drv_unsupported_static_sanitizer_darwin : Error<
   "static %0 runtime is not supported on darwin">;
+def err_drv_not_a_ubsan_sanitizer : Error<"not a UBSan sanitizer: '%0'">;
 def err_drv_duplicate_config : Error<
   "no more than one option '--config' is allowed">;
 def err_drv_cannot_open_config_file : Error<
diff --git a/clang/include/clang/Basic/Features.def 
b/clang/include/clang/Basic/Features.def
index 0e91b42a132c1..52dd3a72392ee 100644
--- a/clang/include/clang/Basic/Features.def
+++ b/clang/include/clang/Basic/Features.def
@@ -53,7 +53,7 @@ FEATURE(memtag_globals,
 LangOpts.Sanitize.has(SanitizerKind::MemtagGlobals))
 FEATURE(xray_instrument, LangOpts.XRayInstrument)
 FEATURE(undefined_behavior_sanitizer,
-LangOpts.Sanitize.hasOneOf(SanitizerKind::Undefined))
+LangOpts.Sanitize.hasOneOf(SanitizerKind::Undefined & 
~LangOpts.UBSanFeatureSuppressedSanitize.Mask))
 FEATURE(undefined_behavior_sanitizer_finegrained_feature_checks, true)
 // These are all part of undefined_behavior_sanitizer:
 FEATURE(alignment_sanitizer,
diff --git a/clang/include/clang/Basic/LangOptions.h 
b/clang/include/clang/Basic/LangOptions.h
index 3f042f8ddb5a1..66fe01e877cb1 100644
--- a/clang/include/clang/Basic/LangOptions.h
+++ b/clang/include/clang/Basic/LangOptions.h
@@ -441,6 +441,9 @@ class LangOptions : public LangOptionsBase {
   SanitizerSet Sanitize;
   /// Is at least one coverage instrumentation type enabled.
   bool SanitizeCoverage = false;
+  /// Set of enabled (undefined behavior) sanitizers that do not cause
+  /// `__has_feature(undefined_behavior_sanitizer)` to evaluate true.
+  SanitizerSet UBSanFeatureSuppressedSanitize;
 
   /// Paths to files specifying which objects
   /// (files, functions, variables) should not be instrumented.
diff --git a/clang/include/clang/Driver/SanitizerArgs.h 
b/clang/include/clang/Driver/SanitizerArgs.h
index 84fb66e16bee3..aa8aa9be287c6 100644
--- a/clang/include/clang/Driver/SanitizerArgs.h
+++ b/clang/include/clang/Driver/SanitizerArgs.h
@@ -28,6 +28,7 @@ class SanitizerArgs {
   SanitizerSet MergeHandlers;
   SanitizerMaskCutoffs SkipHotCutoffs;
   SanitizerSet AnnotateDebugInfo;
+  SanitizerSet SuppressUBSanFeature;
 
   std::vector UserIgnorelistFiles;
   std::vector SystemIgnorelistFiles;
diff --git a/clang/include/clang/Options/Options.td 
b/clang/include/clang/Options/Options.td
index c6841937c8d39..84243ad80f2a1 100644
--- a/clang/include/clang/Options/Options.td
+++ b/clang/include/clang/Options/Options.td
@@ -2404,6 +2404,14 @@ def fsanitize_EQ : CommaJoined<["-"], "fsanitize=">, 
Group,
 "or suspicious behavior. See user manual for 
available checks">;
 def fno_sanitize_EQ : CommaJoined<["-"], "fno-sanitize=">, 
Group,
   Visibility<[ClangOption, CLOption]>;
+def fsanitize_ignore_for_ubsan_feature_EQ
+: CommaJoined<["-"], "fsanitize-ignore-for-ubsan-feature=">,
+  Group,
+  MetaVarName<"">,
+  HelpText<
+  "Prevents `__has_feature(undefined_behavior_sanitizer)` from "
+  "evaluating true for "
+  "these UBSan checks. See user manual for available UBSan checks">;
 
 def fsanitize_ignorelist_EQ : Joined<["-"], "fsanitize-ignorelist=">,
   Group, HelpText<"Path to ignorelist file for sanitizers">;
diff --git a/clang/lib/Driver/SanitizerArgs.cpp 
b/clang/lib/Driver/SanitizerArgs.cpp
index be068b2381d06..08db579626437 100644
--- a/clang/lib/Driver/SanitizerArgs.cpp
+++ b/clang/lib/Driver/SanitizerArgs.cpp
@@ -408,6 +408,8 @@ SanitizerArgs::SanitizerArgs(const ToolChain &TC,
 // unused-argument diagnostics.
   Saniti

[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

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[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

[via cfe-commits]

https://github.com/j39m created https://github.com/llvm/llvm-project/pull/170822

This is a follow-up to pull 148323. It mints
`-fsanitize-ignore-for-ubsan-feature=...`, accepting a list of (UBSan) 
sanitizers that should not cause
`__has_feature(undefined_behavior_sanitizer)` to evaluate true.

>From 30462f19f6ba2bf53eb6440dff018c40282bf3fd Mon Sep 17 00:00:00 2001
From: Kalvin Lee 
Date: Fri, 5 Dec 2025 17:37:29 +0900
Subject: [PATCH] Add fine-grained `__has_feature()` cutout

This is a follow-up to pull 148323. It mints
`-fsanitize-ignore-for-ubsan-feature=...`, accepting a list of (UBSan)
sanitizers that should not cause
`__has_feature(undefined_behavior_sanitizer)` to evaluate true.
---
 .../clang/Basic/DiagnosticDriverKinds.td  |  1 +
 clang/include/clang/Basic/Features.def|  2 +-
 clang/include/clang/Basic/LangOptions.h   |  3 ++
 clang/include/clang/Driver/SanitizerArgs.h|  1 +
 clang/include/clang/Options/Options.td|  8 +
 clang/lib/Driver/SanitizerArgs.cpp| 29 ++
 clang/lib/Frontend/CompilerInvocation.cpp | 15 ++
 ...s_feature_undefined_behavior_sanitizer.cpp | 30 +++
 8 files changed, 88 insertions(+), 1 deletion(-)

diff --git a/clang/include/clang/Basic/DiagnosticDriverKinds.td 
b/clang/include/clang/Basic/DiagnosticDriverKinds.td
index aeffe96e806bd..9e5ca9f76397b 100644
--- a/clang/include/clang/Basic/DiagnosticDriverKinds.td
+++ b/clang/include/clang/Basic/DiagnosticDriverKinds.td
@@ -277,6 +277,7 @@ def err_drv_malformed_sanitizer_metadata_ignorelist : Error<
   "malformed sanitizer metadata ignorelist: '%0'">;
 def err_drv_unsupported_static_sanitizer_darwin : Error<
   "static %0 runtime is not supported on darwin">;
+def err_drv_not_a_ubsan_sanitizer : Error<"not a UBSan sanitizer: '%0'">;
 def err_drv_duplicate_config : Error<
   "no more than one option '--config' is allowed">;
 def err_drv_cannot_open_config_file : Error<
diff --git a/clang/include/clang/Basic/Features.def 
b/clang/include/clang/Basic/Features.def
index 0e91b42a132c1..52dd3a72392ee 100644
--- a/clang/include/clang/Basic/Features.def
+++ b/clang/include/clang/Basic/Features.def
@@ -53,7 +53,7 @@ FEATURE(memtag_globals,
 LangOpts.Sanitize.has(SanitizerKind::MemtagGlobals))
 FEATURE(xray_instrument, LangOpts.XRayInstrument)
 FEATURE(undefined_behavior_sanitizer,
-LangOpts.Sanitize.hasOneOf(SanitizerKind::Undefined))
+LangOpts.Sanitize.hasOneOf(SanitizerKind::Undefined & 
~LangOpts.UBSanFeatureSuppressedSanitize.Mask))
 FEATURE(undefined_behavior_sanitizer_finegrained_feature_checks, true)
 // These are all part of undefined_behavior_sanitizer:
 FEATURE(alignment_sanitizer,
diff --git a/clang/include/clang/Basic/LangOptions.h 
b/clang/include/clang/Basic/LangOptions.h
index 3f042f8ddb5a1..66fe01e877cb1 100644
--- a/clang/include/clang/Basic/LangOptions.h
+++ b/clang/include/clang/Basic/LangOptions.h
@@ -441,6 +441,9 @@ class LangOptions : public LangOptionsBase {
   SanitizerSet Sanitize;
   /// Is at least one coverage instrumentation type enabled.
   bool SanitizeCoverage = false;
+  /// Set of enabled (undefined behavior) sanitizers that do not cause
+  /// `__has_feature(undefined_behavior_sanitizer)` to evaluate true.
+  SanitizerSet UBSanFeatureSuppressedSanitize;
 
   /// Paths to files specifying which objects
   /// (files, functions, variables) should not be instrumented.
diff --git a/clang/include/clang/Driver/SanitizerArgs.h 
b/clang/include/clang/Driver/SanitizerArgs.h
index 84fb66e16bee3..aa8aa9be287c6 100644
--- a/clang/include/clang/Driver/SanitizerArgs.h
+++ b/clang/include/clang/Driver/SanitizerArgs.h
@@ -28,6 +28,7 @@ class SanitizerArgs {
   SanitizerSet MergeHandlers;
   SanitizerMaskCutoffs SkipHotCutoffs;
   SanitizerSet AnnotateDebugInfo;
+  SanitizerSet SuppressUBSanFeature;
 
   std::vector UserIgnorelistFiles;
   std::vector SystemIgnorelistFiles;
diff --git a/clang/include/clang/Options/Options.td 
b/clang/include/clang/Options/Options.td
index c6841937c8d39..84243ad80f2a1 100644
--- a/clang/include/clang/Options/Options.td
+++ b/clang/include/clang/Options/Options.td
@@ -2404,6 +2404,14 @@ def fsanitize_EQ : CommaJoined<["-"], "fsanitize=">, 
Group,
 "or suspicious behavior. See user manual for 
available checks">;
 def fno_sanitize_EQ : CommaJoined<["-"], "fno-sanitize=">, 
Group,
   Visibility<[ClangOption, CLOption]>;
+def fsanitize_ignore_for_ubsan_feature_EQ
+: CommaJoined<["-"], "fsanitize-ignore-for-ubsan-feature=">,
+  Group,
+  MetaVarName<"">,
+  HelpText<
+  "Prevents `__has_feature(undefined_behavior_sanitizer)` from "
+  "evaluating true for "
+  "these UBSan checks. See user manual for available UBSan checks">;
 
 def fsanitize_ignorelist_EQ : Joined<["-"], "fsanitize-ignorelist=">,
   Group, HelpText<"Path to ignorelist file for sanitizers">;
diff --git a/clang/lib/Driver/Sanitize