chill created this revision.
chill added reviewers: rsmith, aaron.ballman.
Executing the following program
#include <cassert>
#include <cstddef>
struct S {
char x;
int y;
} __attribute__((packed, aligned(8)));
struct alignas(8) T {
char x;
int y;
} __attribute__((packed));
int main() {
assert(offsetof(S, x) == 0);
assert(offsetof(S, y) == 1);
assert(offsetof(T, x) == 0);
assert(offsetof(T, y) == 1);
}
fails with assertion
a.out: a.cc:19: int main(): Assertion `offsetof(T, y) == 1' failed.
The layout if `T` is incorrect, because it's computed and effectively cached
when checking for `alignas` under-aligning the structure, however, this happens
before `__attribute__((packed))` is processed.
This patch moves the processing of attributes before the `alignas`
under-alignment check.
Repository:
rC Clang
https://reviews.llvm.org/D46439
Files:
lib/Sema/SemaDecl.cpp
Index: lib/Sema/SemaDecl.cpp
===================================================================
--- lib/Sema/SemaDecl.cpp
+++ lib/Sema/SemaDecl.cpp
@@ -15573,6 +15573,10 @@
if (!Completed)
Record->completeDefinition();
+ // Handle attributes before checking for alignas underalignment.
+ if (Attr)
+ ProcessDeclAttributeList(S, Record, Attr);
+
// We may have deferred checking for a deleted destructor. Check now.
if (CXXRecordDecl *CXXRecord = dyn_cast<CXXRecordDecl>(Record)) {
auto *Dtor = CXXRecord->getDestructor();
@@ -15703,9 +15707,6 @@
CDecl->setIvarRBraceLoc(RBrac);
}
}
-
- if (Attr)
- ProcessDeclAttributeList(S, Record, Attr);
}
/// \brief Determine whether the given integral value is representable within
Index: lib/Sema/SemaDecl.cpp
===================================================================
--- lib/Sema/SemaDecl.cpp
+++ lib/Sema/SemaDecl.cpp
@@ -15573,6 +15573,10 @@
if (!Completed)
Record->completeDefinition();
+ // Handle attributes before checking for alignas underalignment.
+ if (Attr)
+ ProcessDeclAttributeList(S, Record, Attr);
+
// We may have deferred checking for a deleted destructor. Check now.
if (CXXRecordDecl *CXXRecord = dyn_cast<CXXRecordDecl>(Record)) {
auto *Dtor = CXXRecord->getDestructor();
@@ -15703,9 +15707,6 @@
CDecl->setIvarRBraceLoc(RBrac);
}
}
-
- if (Attr)
- ProcessDeclAttributeList(S, Record, Attr);
}
/// \brief Determine whether the given integral value is representable within
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