[PATCH] D43908: [RecordLayout] Only assert that fundamental type sizes are power of two on MSVC
Martin Storsjö via Phabricator via cfe-commits
cfe-commits at lists.llvm.org
Thu Mar 1 00:10:34 PST 2018
mstorsjo updated this revision to Diff 136471.
mstorsjo edited the summary of this revision.
mstorsjo added a comment.
Added an error-by-default diagnostic (just like the existing warn_cxx_ms_struct) for this case, trigger it on all targets other than mingw (where the situation is quite likely to occur, and GCC handles it silently).
@compnerd, do you like this better?
https://reviews.llvm.org/D43908
Files:
include/clang/Basic/DiagnosticSemaKinds.td
lib/AST/RecordLayoutBuilder.cpp
test/CodeGen/ms_struct-long-double.c
Index: test/CodeGen/ms_struct-long-double.c
===================================================================
--- /dev/null
+++ test/CodeGen/ms_struct-long-double.c
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -emit-llvm-only -triple i686-windows-gnu -fdump-record-layouts %s | FileCheck %s
+// RUN: %clang_cc1 -emit-llvm-only -triple i686-linux -fdump-record-layouts -Wno-incompatible-ms-struct %s | FileCheck %s
+// RUN: not %clang_cc1 -emit-llvm-only -triple i686-linux -fdump-record-layouts %s 2>&1 | FileCheck %s -check-prefix=ERROR
+
+struct ldb_struct {
+ char c;
+ long double ldb;
+} __attribute__((__ms_struct__));
+
+struct ldb_struct a;
+
+// CHECK: 0 | struct ldb_struct
+// CHECK-NEXT: 0 | char c
+// CHECK-NEXT: 4 | long double ldb
+// CHECK-NEXT: | [sizeof=16, align=4]
+
+// ERROR: error: ms_struct may not produce Microsoft-compatible layouts with fundamental data types with sizes that aren't a power of two
Index: lib/AST/RecordLayoutBuilder.cpp
===================================================================
--- lib/AST/RecordLayoutBuilder.cpp
+++ lib/AST/RecordLayoutBuilder.cpp
@@ -1752,10 +1752,32 @@
QualType T = Context.getBaseElementType(D->getType());
if (const BuiltinType *BTy = T->getAs<BuiltinType>()) {
CharUnits TypeSize = Context.getTypeSizeInChars(BTy);
- assert(
- (llvm::isPowerOf2_64(TypeSize.getQuantity()) ||
- Context.getTargetInfo().getTriple().isWindowsGNUEnvironment()) &&
- "Non PowerOf2 size outside of GNU mode");
+
+ if (!llvm::isPowerOf2_64(TypeSize.getQuantity())) {
+ assert(
+ !Context.getTargetInfo().getTriple().isWindowsMSVCEnvironment() &&
+ "Non PowerOf2 size in MSVC mode");
+ // Base types with sizes that aren't a power of two don't work
+ // with the layout rules for MS structs. This isn't an issue in
+ // MSVC itself since there are no such base data types there.
+ // On e.g. x86_32 mingw and linux, long double is 12 bytes though.
+ // Any structs involving that data type obviously can't be ABI
+ // compatible with MSVC regardless of how it is laid out.
+
+ // Since ms_struct can be mass enabled (via a pragma or via the
+ // -mms-bitfields command line parameter), this can trigger for
+ // structs that don't actually need MSVC compatibility, so we
+ // need to be able to sidestep the ms_struct layout for these types.
+
+ // Since the combination of -mms-bitfields together with structs
+ // like max_align_t (which contains a long double) for mingw is
+ // quite comon (and GCC handles it silently), just handle it
+ // silently there. For other targets that have ms_struct enabled
+ // (most probably via a pragma or attribute), trigger a diagnostic
+ // that defaults to an error.
+ if (!Context.getTargetInfo().getTriple().isWindowsGNUEnvironment())
+ Diag(D->getLocation(), diag::warn_npot_ms_struct);
+ }
if (TypeSize > FieldAlign &&
llvm::isPowerOf2_64(TypeSize.getQuantity()))
FieldAlign = TypeSize;
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -759,6 +759,10 @@
Warning<"ms_struct may not produce Microsoft-compatible layouts for classes "
"with base classes or virtual functions">,
DefaultError, InGroup<IncompatibleMSStruct>;
+def warn_npot_ms_struct :
+ Warning<"ms_struct may not produce Microsoft-compatible layouts with fundamental "
+ "data types with sizes that aren't a power of two">,
+ DefaultError, InGroup<IncompatibleMSStruct>;
def err_section_conflict : Error<"%0 causes a section type conflict with %1">;
def err_no_base_classes : Error<"invalid use of '__super', %0 has no base classes">;
def err_invalid_super_scope : Error<"invalid use of '__super', "
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