perf: update free_sized declaration to be compatible with glibc (#8661)

glibc adds `__attribute__((nothrow))` to its declarations, at least for
those related to malloc. glibc has yet to introduce `free_sized`, but
when it does it would cause compilation errors. This is due to the fact
that if a function declarations has `__attribute__((nothrow))` and it is
re-declared or implemented in C++ it must also have
`__attribute__((nothrow))` or `noexcept`, otherwise the compilation will
fail.

This is a follow up to #6598.

Signed-off-by: Justin King <[email protected]>

Author: jcking

src/include/lean/lean.h

@@ -416,6 +416,11 @@ void free(void *);  // avoid including big `stdlib.h`
 #endif
 
 #if !defined(__STDC_VERSION_STDLIB_H__) || __STDC_VERSION_STDLIB_H__ < 202311L
+#if defined(__GLIBC__) && (defined(__GNUC__) || defined(__clang__))
+// glibc tacks on `__attribute__((nothrow))` to its declarations. In C++ this requires either
+// `__attribute__((nothrow))` to be present or `noexcept`.
+__attribute__((nothrow))
+#endif
 void free_sized(void* ptr, size_t);
 #endif
 

src/runtime/object.cpp

@@ -48,7 +48,13 @@ Author: Leonardo de Moura
 #endif
 
 #if !defined(__STDC_VERSION_STDLIB_H__) || __STDC_VERSION_STDLIB_H__ < 202311L
-extern "C" LEAN_EXPORT __attribute__((weak)) void free_sized(void *ptr, size_t) {
+extern "C" LEAN_EXPORT
+#if defined(__GLIBC__) && (defined(__GNUC__) || defined(__clang__))
+// glibc tacks on `__attribute__((nothrow))` to its declarations. In C++ this requires either
+// `__attribute__((nothrow))` to be present or `noexcept`.
+__attribute__((nothrow))
+#endif
+__attribute__((weak)) void free_sized(void *ptr, size_t) {
     free(ptr);
 }
 #endif