On Tue, 9 Jan 2024 at 22:00, Jonathan Wakely wrote: > > Does anybody see any problem with making this change, so that we avoid > the problem described in the PR?
Pushed to trunk. We should backport this too. > > -- >8 -- > > As described in PR libstdc++/113258 there are old versions of tcmalloc > which replace malloc and related APIs, but do not repalce aligned_alloc > because it didn't exist at the time they were released. This means that > when operator new(size_t, align_val_t) uses aligned_alloc to obtain > memory, it comes from libc's aligned_alloc not from tcmalloc. But when > operator delete(void*, size_t, align_val_t) uses free to deallocate the > memory, that goes to tcmalloc's replacement version of free, which > doesn't know how to free it. > > If we give preference to the older posix_memalign instead of > aligned_alloc then we're more likely to use a function that will be > compatible with the replacement version of free. Because posix_memalign > has been around for longer, it's more likely that old third-party malloc > replacements will also replace posix_memalign alongside malloc and free. > > libstdc++-v3/ChangeLog: > > PR libstdc++/113258 > * libsupc++/new_opa.cc: Prefer to use posix_memalign if > available. > --- > libstdc++-v3/libsupc++/new_opa.cc | 26 +++++++++++++++----------- > 1 file changed, 15 insertions(+), 11 deletions(-) > > diff --git a/libstdc++-v3/libsupc++/new_opa.cc > b/libstdc++-v3/libsupc++/new_opa.cc > index 8326b7497fe..35606e1c1b3 100644 > --- a/libstdc++-v3/libsupc++/new_opa.cc > +++ b/libstdc++-v3/libsupc++/new_opa.cc > @@ -46,12 +46,12 @@ using std::bad_alloc; > using std::size_t; > extern "C" > { > -# if _GLIBCXX_HAVE_ALIGNED_ALLOC > +# if _GLIBCXX_HAVE_POSIX_MEMALIGN > + void *posix_memalign(void **, size_t alignment, size_t size); > +# elif _GLIBCXX_HAVE_ALIGNED_ALLOC > void *aligned_alloc(size_t alignment, size_t size); > # elif _GLIBCXX_HAVE__ALIGNED_MALLOC > void *_aligned_malloc(size_t size, size_t alignment); > -# elif _GLIBCXX_HAVE_POSIX_MEMALIGN > - void *posix_memalign(void **, size_t alignment, size_t size); > # elif _GLIBCXX_HAVE_MEMALIGN > void *memalign(size_t alignment, size_t size); > # else > @@ -63,13 +63,10 @@ extern "C" > #endif > > namespace __gnu_cxx { > -#if _GLIBCXX_HAVE_ALIGNED_ALLOC > -using ::aligned_alloc; > -#elif _GLIBCXX_HAVE__ALIGNED_MALLOC > -static inline void* > -aligned_alloc (std::size_t al, std::size_t sz) > -{ return _aligned_malloc(sz, al); } > -#elif _GLIBCXX_HAVE_POSIX_MEMALIGN > +// Prefer posix_memalign if available, because it's older than aligned_alloc > +// and so more likely to be provided by replacement malloc libraries that > +// predate the addition of aligned_alloc. See PR libstdc++/113258. > +#if _GLIBCXX_HAVE_POSIX_MEMALIGN > static inline void* > aligned_alloc (std::size_t al, std::size_t sz) > { > @@ -83,6 +80,12 @@ aligned_alloc (std::size_t al, std::size_t sz) > return ptr; > return nullptr; > } > +#elif _GLIBCXX_HAVE_ALIGNED_ALLOC > +using ::aligned_alloc; > +#elif _GLIBCXX_HAVE__ALIGNED_MALLOC > +static inline void* > +aligned_alloc (std::size_t al, std::size_t sz) > +{ return _aligned_malloc(sz, al); } > #elif _GLIBCXX_HAVE_MEMALIGN > static inline void* > aligned_alloc (std::size_t al, std::size_t sz) > @@ -128,7 +131,8 @@ operator new (std::size_t sz, std::align_val_t al) > if (__builtin_expect (sz == 0, false)) > sz = 1; > > -#if _GLIBCXX_HAVE_ALIGNED_ALLOC > +#if _GLIBCXX_HAVE_POSIX_MEMALIGN > +#elif _GLIBCXX_HAVE_ALIGNED_ALLOC > # if defined _AIX || defined __APPLE__ > /* AIX 7.2.0.0 aligned_alloc incorrectly has posix_memalign's requirement > * that alignment is a multiple of sizeof(void*). > -- > 2.43.0 >