[libcxx] Support providing symbol suffix through compiler define #122570
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When -funique-internal-linkage-names option is enabled, Clang will append a unique suffix `.uniq.<MD5 hash of the source file>` to all internal symbols. Since we cannot detect when this option is enabled or compute the source file hash from within the source file itself, the unique suffix needs to be supplied by the build system. The `_LIBCPP_SYMBOL_SUFFIX` can be used for that purpose.
petrhosek
added
the
libc++
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@llvm/pr-subscribers-libcxx Author: Petr Hosek (petrhosek) ChangesWhen -funique-internal-linkage-names option is enabled, Clang will append a unique suffix Full diff: https://github.com/llvm/llvm-project/pull/122570.diff 1 Files Affected:
diff --git a/libcxx/src/include/overridable_function.h b/libcxx/src/include/overridable_function.h
index 7372e347831bb4..7eee4ecd06a98d 100644
--- a/libcxx/src/include/overridable_function.h
+++ b/libcxx/src/include/overridable_function.h
@@ -56,6 +56,15 @@
// with this macro must be defined at global scope.
//
+// When -funique-internal-linkage-names option is enabled, Clang will append a unique suffix
+// `.uniq.<MD5 hash of the source file>` to all internal symbols. Since we cannot detect when
+// this option is enabled or compute the source file hash from within the source file itself,
+// the unique suffix needs to be supplied by the build system. The `_LIBCPP_SYMBOL_SUFFIX` can
+// be used for that purpose.
+#ifndef _LIBCPP_SYMBOL_SUFFIX
+#define _LIBCPP_SYMBOL_SUFFIX
+#endif
+
#if defined(_LIBCPP_OBJECT_FORMAT_MACHO)
_LIBCPP_BEGIN_NAMESPACE_STD
@@ -68,8 +77,8 @@ _LIBCPP_END_NAMESPACE_STD
# define _LIBCPP_CAN_DETECT_OVERRIDDEN_FUNCTION 1
# define _LIBCPP_OVERRIDABLE_FUNCTION(symbol, type, name, arglist) \
static __attribute__((used)) type symbol##_impl__ arglist __asm__("_" _LIBCPP_TOSTRING(symbol)); \
- __asm__(".globl _" _LIBCPP_TOSTRING(symbol)); \
- __asm__(".weak_definition _" _LIBCPP_TOSTRING(symbol)); \
+ __asm__(".globl _" _LIBCPP_TOSTRING(symbol) _LIBCPP_SYMBOL_SUFFIX); \
+ __asm__(".weak_definition _" _LIBCPP_TOSTRING(symbol) _LIBCPP_SYMBOL_SUFFIX); \
extern __typeof(symbol##_impl__) name __attribute__((weak_import)); \
_LIBCPP_BEGIN_NAMESPACE_STD \
template <> \
@@ -91,7 +100,7 @@ _LIBCPP_END_NAMESPACE_STD
# define _LIBCPP_CAN_DETECT_OVERRIDDEN_FUNCTION 1
# define _LIBCPP_OVERRIDABLE_FUNCTION(symbol, type, name, arglist) \
static type symbol##_impl__ arglist __asm__(_LIBCPP_TOSTRING(symbol##_impl__)); \
- [[gnu::weak, gnu::alias(_LIBCPP_TOSTRING(symbol##_impl__))]] type name arglist; \
+ [[gnu::weak, gnu::alias(_LIBCPP_TOSTRING(symbol##_impl__) _LIBCPP_SYMBOL_SUFFIX)]] type name arglist; \
_LIBCPP_BEGIN_NAMESPACE_STD \
template <> \
inline bool __is_function_overridden<static_cast<type(*) arglist>(name)>() { \
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You can test this locally with the following command:git-clang-format --diff 833a17489dd96f35df3a17ad231ada82acf38ef9 f1e0e27ba9db807ae9f1471323193852500be781 --extensions h -- libcxx/src/include/overridable_function.hView the diff from clang-format here.diff --git a/libcxx/src/include/overridable_function.h b/libcxx/src/include/overridable_function.h
index 9071140516..ed3a3062af 100644
--- a/libcxx/src/include/overridable_function.h
+++ b/libcxx/src/include/overridable_function.h
@@ -62,7 +62,7 @@
// the unique suffix needs to be supplied by the build system. The `_LIBCPP_SYMBOL_SUFFIX` can
// be used for that purpose.
#ifndef _LIBCPP_SYMBOL_SUFFIX
-#define _LIBCPP_SYMBOL_SUFFIX
+# define _LIBCPP_SYMBOL_SUFFIX
#endif
#if defined(_LIBCPP_OBJECT_FORMAT_MACHO)
@@ -100,7 +100,7 @@ _LIBCPP_END_NAMESPACE_STD
# define _LIBCPP_CAN_DETECT_OVERRIDDEN_FUNCTION 1
# define _LIBCPP_OVERRIDABLE_FUNCTION(symbol, type, name, arglist) \
static type symbol##_impl__ arglist __asm__(_LIBCPP_TOSTRING(symbol##_impl__) _LIBCPP_SYMBOL_SUFFIX); \
- [[gnu::weak, gnu::alias(_LIBCPP_TOSTRING(symbol##_impl__) _LIBCPP_SYMBOL_SUFFIX)]] type name arglist; \
+ [[ gnu::weak, gnu::alias(_LIBCPP_TOSTRING(symbol##_impl__) _LIBCPP_SYMBOL_SUFFIX) ]] type name arglist; \
_LIBCPP_BEGIN_NAMESPACE_STD \
template <> \
inline bool __is_function_overridden<static_cast<type(*) arglist>(name)>() { \
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ldionne
requested changes
Jan 16, 2025
| @@ -56,6 +56,15 @@ | |||
| // with this macro must be defined at global scope. | |||
| // | |||
|
|
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| // When -funique-internal-linkage-names option is enabled, Clang will append a unique suffix | |||
There was a problem hiding this comment.
It sounds like a generally missing feature that Clang doesn't provide any way to access that. I would prefer if we instead introduced either a macro that contains this suffix, or even better some kind of __builtin_symbol_name(name) that returns a string representing the symbol name for that entity while taking into account -funique-internal-linkage-names if needed.
That's something we could also use when defining operator new itself, i.e. we would not have to hardcode the mangled name in the macro. Similarly, we could refactor horrors like https://github.com/llvm/llvm-project/blob/main/libcxx/src/iostream.cpp#L22 where we hardcode mangled names, something @philnik777 was looking to do recently.
WDYT?
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When -funique-internal-linkage-names option is enabled, Clang will append a unique suffix
.uniq.<MD5 hash of the source file>to all internal symbols. Since we cannot detect when this option is enabled or compute the source file hash from within the source file itself, the unique suffix needs to be supplied by the build system. The_LIBCPP_SYMBOL_SUFFIXcan be used for that purpose.