[devkitPPC] ::aligned_alloc is available, but not std::aligned_alloc

[dkosmari]

I'm reporting this here, since the gcc repo doesn't allow submitting issues.

In devkitPPC/powerpc-eabi/include/c++/13.2.0/powerpc-eabi/bits/c++config.h, the _GLIBCXX_HAVE_ALIGNED_ALLOC macro is not defined, and that prevents the C function aligned_alloc() to be imported into the std namespace for C++ (in cstdlib).

This code compiles:

#include <stdlib.h>
// ...
buffer = ::aligned_alloc(256, size);

but this doesn't:

#include <cstdlib>
// ...
buffer = std::aligned_alloc(256, size);

[WinterMute]

The same error occurs for me on linux, mingw64 and macOS with both g++ and clang suggesting this usage isn't portable. Where is this a problem?

[WinterMute]

Further investigation shows -std=c++17 is necessary for my linux & macOS compilers to compile this test code

#include <cstdlib>
#include <cstdio>

int main(int argc, char **argv) {

	printf("alloc is %p\n", std::aligned_alloc(256, 1024));
	return 0;
}

Still won't work with mingw64 and, from what I can see here, won't work with other newlib based toolchains without patching. I do have a fix for this though which I'll apply for next release.

[dkosmari]

From inspecting the libstdc++v3 configuration scripts, I think it's simply missing a AC_CHECK_FUNCS(aligned_alloc posix_memalign memalign _aligned_malloc), or the corresponding AC_DEFINE, in the non-native path. A lot of these function checks are hardcoded in crossconfig.m4 for each target, so it's expected for features to be missing until somebody manually patches them in.