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Add -fcheck-new and -fno-check-new, from GCC, which make the compiler
not assume pointers returned from operator new are non-null.
Fixes #16931.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D125272
Files:
clang/include/clang/Basic/LangOptions.def
clang/include/clang/Basic/LangOptions.h
clang/include/clang/Driver/Options.td
clang/lib/AST/ExprCXX.cpp
clang/lib/Driver/ToolChains/Clang.cpp
clang/lib/Frontend/CompilerInvocation.cpp
clang/lib/Sema/SemaDecl.cpp
clang/lib/Sema/SemaExprCXX.cpp
clang/test/CodeGenCXX/fcheck-new.cpp
clang/test/Driver/clang_f_opts.c
Index: clang/test/Driver/clang_f_opts.c
===================================================================
--- clang/test/Driver/clang_f_opts.c
+++ clang/test/Driver/clang_f_opts.c
@@ -70,7 +70,6 @@
// CHECK-CUDA-SAMPLE-PROFILE: "-cc1"
// CHECK-CUDA-SAMPLE-PROFILE-SAME: "-fprofile-sample-use={{.*}}/file.prof"
-
// RUN: %clang -### -S -fauto-profile=%S/Inputs/file.prof %s 2>&1 | FileCheck -check-prefix=CHECK-AUTO-PROFILE %s
// CHECK-AUTO-PROFILE: "-fprofile-sample-use={{.*}}/file.prof"
@@ -298,7 +297,6 @@
// RUN: -fno-reorder-blocks -freorder-blocks \
// RUN: -fno-schedule-insns2 -fschedule-insns2 \
// RUN: -fno-stack-check \
-// RUN: -fno-check-new -fcheck-new \
// RUN: -ffriend-injection \
// RUN: -fno-implement-inlines -fimplement-inlines \
// RUN: -fstack-check \
Index: clang/test/CodeGenCXX/fcheck-new.cpp
===================================================================
--- /dev/null
+++ clang/test/CodeGenCXX/fcheck-new.cpp
@@ -0,0 +1,20 @@
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py
+// RUN: %clang -fcheck-new -emit-llvm -S %s -o - -O2 | FileCheck %s
+
+// CHECK-LABEL: @_Z5test0v(
+// CHECK-NEXT: [[TMP1:%.*]] = tail call noalias noundef dereferenceable_or_null(4) ptr @_Znwm(i64 noundef 4) #[[ATTR2:[0-9]+]]
+// CHECK-NEXT: [[TMP2:%.*]] = icmp eq ptr [[TMP1]], null
+// CHECK-NEXT: br i1 [[TMP2]], label [[TMP4:%.*]], label [[TMP3:%.*]]
+// CHECK: 3:
+// CHECK-NEXT: store i32 48879, ptr [[TMP1]], align 4, !tbaa [[TBAA5:![0-9]+]]
+// CHECK-NEXT: br label [[TMP4]]
+// CHECK: 4:
+// CHECK-NEXT: ret ptr [[TMP1]]
+//
+int *test0() {
+ int *ptr = new int;
+ if (!ptr)
+ return (int *)0;
+ *ptr = 0xbeef;
+ return ptr;
+}
Index: clang/lib/Sema/SemaExprCXX.cpp
===================================================================
--- clang/lib/Sema/SemaExprCXX.cpp
+++ clang/lib/Sema/SemaExprCXX.cpp
@@ -3104,7 +3104,8 @@
// Global allocation functions should always be visible.
Alloc->setVisibleDespiteOwningModule();
- if (HasBadAllocExceptionSpec && getLangOpts().NewInfallible)
+ if (HasBadAllocExceptionSpec && getLangOpts().NewInfallible &&
+ !getLangOpts().CheckNew)
Alloc->addAttr(
ReturnsNonNullAttr::CreateImplicit(Context, Alloc->getLocation()));
Index: clang/lib/Sema/SemaDecl.cpp
===================================================================
--- clang/lib/Sema/SemaDecl.cpp
+++ clang/lib/Sema/SemaDecl.cpp
@@ -15436,7 +15436,11 @@
// indicates failure by returning a null pointer value. Any other allocation
// function never returns a null pointer value and indicates failure only by
// throwing an exception [...]
- if (!IsNothrow && !FD->hasAttr<ReturnsNonNullAttr>())
+ //
+ // However, -fcheck-new violates this possible assumption, so don't add
+ // NonNull when that is enabled.
+ if (!IsNothrow && !FD->hasAttr<ReturnsNonNullAttr>() &&
+ !getLangOpts().CheckNew)
FD->addAttr(ReturnsNonNullAttr::CreateImplicit(Context, FD->getLocation()));
// C++2a [basic.stc.dynamic.allocation]p2:
Index: clang/lib/Frontend/CompilerInvocation.cpp
===================================================================
--- clang/lib/Frontend/CompilerInvocation.cpp
+++ clang/lib/Frontend/CompilerInvocation.cpp
@@ -4113,6 +4113,9 @@
if (const Arg *A = Args.getLastArg(OPT_frandomize_layout_seed_EQ))
Opts.RandstructSeed = A->getValue(0);
+ if (const Arg *A = Args.getLastArg(OPT_fcheck_new))
+ Opts.CheckNew = true;
+
return Diags.getNumErrors() == NumErrorsBefore;
}
Index: clang/lib/Driver/ToolChains/Clang.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Clang.cpp
+++ clang/lib/Driver/ToolChains/Clang.cpp
@@ -5981,6 +5981,9 @@
options::OPT_fno_emulated_tls);
Args.AddLastArg(CmdArgs, options::OPT_fzero_call_used_regs_EQ);
+ if (Args.hasFlag(options::OPT_fcheck_new, options::OPT_fno_check_new, false))
+ CmdArgs.push_back("-fcheck-new");
+
if (Arg *A = Args.getLastArg(options::OPT_fzero_call_used_regs_EQ)) {
// FIXME: There's no reason for this to be restricted to X86. The backend
// code needs to be changed to include the appropriate function calls
Index: clang/lib/AST/ExprCXX.cpp
===================================================================
--- clang/lib/AST/ExprCXX.cpp
+++ clang/lib/AST/ExprCXX.cpp
@@ -275,6 +275,8 @@
}
bool CXXNewExpr::shouldNullCheckAllocation() const {
+ if (getOperatorNew()->getLangOpts().CheckNew)
+ return true;
return !getOperatorNew()->hasAttr<ReturnsNonNullAttr>() &&
getOperatorNew()
->getType()
Index: clang/include/clang/Driver/Options.td
===================================================================
--- clang/include/clang/Driver/Options.td
+++ clang/include/clang/Driver/Options.td
@@ -4579,7 +4579,11 @@
// ignore it for now to avoid breaking builds that use it.
def fdiagnostics_show_location_EQ : Joined<["-"], "fdiagnostics-show-location=">, Group<clang_ignored_f_Group>;
-defm fcheck_new : BooleanFFlag<"check-new">, Group<clang_ignored_f_Group>;
+defm check_new : BoolFOption<"check-new",
+ LangOpts<"CheckNew">, DefaultFalse,
+ PosFlag<SetTrue, [], "Check for a null pointer before using storage allocated by new">,
+ NegFlag<SetFalse>, BothFlags<[CC1Option]>>;
+
defm caller_saves : BooleanFFlag<"caller-saves">, Group<clang_ignored_gcc_optimization_f_Group>;
defm reorder_blocks : BooleanFFlag<"reorder-blocks">, Group<clang_ignored_gcc_optimization_f_Group>;
defm branch_count_reg : BooleanFFlag<"branch-count-reg">, Group<clang_ignored_gcc_optimization_f_Group>;
Index: clang/include/clang/Basic/LangOptions.h
===================================================================
--- clang/include/clang/Basic/LangOptions.h
+++ clang/include/clang/Basic/LangOptions.h
@@ -452,6 +452,10 @@
/// The seed used by the randomize structure layout feature.
std::string RandstructSeed;
+ // Indicates whether we should keep all nullptr checks for pointers
+ // received as a result of a standard operator new (-fcheck-new)
+ bool CheckNew = false;
+
LangOptions();
/// Set language defaults for the given input language and
Index: clang/include/clang/Basic/LangOptions.def
===================================================================
--- clang/include/clang/Basic/LangOptions.def
+++ clang/include/clang/Basic/LangOptions.def
@@ -443,6 +443,8 @@
VALUE_LANGOPT(FuchsiaAPILevel, 32, 0, "Fuchsia API level")
+BENIGN_LANGOPT(CheckNew, 1, 0, "Do not eliminate null pointer checks for storage allocated by new")
+
#undef LANGOPT
#undef COMPATIBLE_LANGOPT
#undef BENIGN_LANGOPT
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