[PATCH] D151753: [Clang][Sema] Do not try to analyze dependent alignment during -Wcast-align

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serge-sans-paille created this revision.
serge-sans-paille added reviewers: dim, Fznamznon.
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Fix #63007


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D151753

Files:
  clang/lib/Sema/SemaChecking.cpp
  clang/test/SemaCXX/warn-cast-align.cpp


Index: clang/test/SemaCXX/warn-cast-align.cpp
===================================================================
--- clang/test/SemaCXX/warn-cast-align.cpp
+++ clang/test/SemaCXX/warn-cast-align.cpp
@@ -44,6 +44,11 @@
   c = IntPtr(P);
 }
 
+template <class A> void DependentAlign() {
+  alignas(A) int lut[]{};
+  (long *)lut; // expected-warning {{cast from 'int *' to 'long *'}}
+}
+
 struct __attribute__((aligned(16))) AlignedS {
   char m[16];
 };
Index: clang/lib/Sema/SemaChecking.cpp
===================================================================
--- clang/lib/Sema/SemaChecking.cpp
+++ clang/lib/Sema/SemaChecking.cpp
@@ -16158,8 +16158,13 @@
     if (auto *VD = dyn_cast<VarDecl>(cast<DeclRefExpr>(E)->getDecl())) {
       // FIXME: If VD is captured by copy or is an escaping __block variable,
       // use the alignment of VD's type.
-      if (!VD->getType()->isReferenceType())
+      if (!VD->getType()->isReferenceType()) {
+        // Dependent alignment cannot be resolved -> bail out.
+        if (any_of(VD->specific_attrs<AlignedAttr>(),
+                   [](auto *A) { return A->isAlignmentDependent(); }))
+          break;
         return std::make_pair(Ctx.getDeclAlign(VD), CharUnits::Zero());
+      }
       if (VD->hasInit())
         return getBaseAlignmentAndOffsetFromLValue(VD->getInit(), Ctx);
     }



Index: clang/test/SemaCXX/warn-cast-align.cpp
===================================================================
--- clang/test/SemaCXX/warn-cast-align.cpp
+++ clang/test/SemaCXX/warn-cast-align.cpp
@@ -44,6 +44,11 @@
   c = IntPtr(P);
 }
 
+template <class A> void DependentAlign() {
+  alignas(A) int lut[]{};
+  (long *)lut; // expected-warning {{cast from 'int *' to 'long *'}}
+}
+
 struct __attribute__((aligned(16))) AlignedS {
   char m[16];
 };
Index: clang/lib/Sema/SemaChecking.cpp
===================================================================
--- clang/lib/Sema/SemaChecking.cpp
+++ clang/lib/Sema/SemaChecking.cpp
@@ -16158,8 +16158,13 @@
     if (auto *VD = dyn_cast<VarDecl>(cast<DeclRefExpr>(E)->getDecl())) {
       // FIXME: If VD is captured by copy or is an escaping __block variable,
       // use the alignment of VD's type.
-      if (!VD->getType()->isReferenceType())
+      if (!VD->getType()->isReferenceType()) {
+        // Dependent alignment cannot be resolved -> bail out.
+        if (any_of(VD->specific_attrs<AlignedAttr>(),
+                   [](auto *A) { return A->isAlignmentDependent(); }))
+          break;
         return std::make_pair(Ctx.getDeclAlign(VD), CharUnits::Zero());
+      }
       if (VD->hasInit())
         return getBaseAlignmentAndOffsetFromLValue(VD->getInit(), Ctx);
     }

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