Fork#40315: c++17 std::aligned_alloc
Open Date: 2020-04-10 05:55
Last Update: 2020-04-11 17:18
URL for this Ticket:
https://osdn.net//projects/mingw/ticket/40315
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Last Changes/Comment on this Ticket:
2020-04-11 17:18 Updated by: keith
Comment:
Reply To drakbar
I am not sure if this helps, but it seems that GCC version 7.4 implemented
this.
Likely when they implemented ISO-C11, or maybe just ISO-C++17 support; (I
erroneously referred to ISO-C99, but aligned_alloc() support was added later).
However, that GCC support was likely restricted to POSIX.1 compliant platforms,
which windows is not.
Now I realize that a GCC in a browser is different than a GCC on windows,
but I guess I am a bit confused.
Huh? GCC doesn't (normally) run in a browser; it runs on a variety of host
platforms, but primarily those which are POSIX.1 compliant.
I was under the impression that upstream GCC wouldn't be concerned if it
works on windows.
Upstream has supported mingw32 for years, but never as a primary target. For
GCC-3.4.5, it was a secondary target; today it may have been demoted to
tertiary. However, that's bye-the-bye: a MinGW.org release is no more than our
binary build from upstream source — with a few local patches — but
aligned_alloc() is difficult to implement, because Microsoft's underlying APIs
are incompatible with its standardized requirements; (see the other ticket, to
which I referred you). Welcome to the world of programming on windows; you
often have to work around Microsoft's violation of standards. In the case of
aligned_alloc(), you may need to consider _aligned_malloc(), (which you then
need to pair with _aligned_free()).
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Ticket Status:
Reporter: drakbar
Owner: (None)
Type: Issues
Status: Open
Priority: 5 - Medium
MileStone: (None)
Component: GCC
Severity: 5 - Medium
Resolution: None
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Ticket details:
According to cppreference, the function std::aligned_alloc is apart of C++17.
When trying to compile the example code found at that page, the following
compilation error occurs:
src code
1. #include <cstdio>
2. #include <cstdlib>
3.
4. int main()
5. {
6. int* p1 = static_cast<int*>(std::malloc(10*sizeof *p1));
7. std::printf("default-aligned address: %p\n", static_cast<void*>(p1));
8. std::free(p1);
9.
10. int* p2 = static_cast<int*>(std::aligned_alloc(1024, 1024));
11. std::printf("1024-byte aligned address: %p\n", static_cast<void*>(p2));
12. std::free(p2);
13. }
compilation output
$g++ -std=c++17 alignment.cpp -o main
alignment.cpp: In function 'int main()':
alignment.cpp:10:38: error: 'aligned_alloc' is not a member of 'std'
10 | int* p2 = static_cast<int*>(std::aligned_alloc(1024, 1024));
gcc version
Target: x86_64-w64-mingw32
Configured with: ../gcc-9.3.0/configure --prefix=/mingw64 --with-local-prefix=/mingw64/local --build=x86_64-w64-mingw32 --host=x86_64-w64-mingw32 --target=x86_64-w64-mingw32 --with-native-system-header-dir=/mingw64/x86_64-w64-mingw32/include --libexecdir=/mingw64/lib --enable-bootstrap --with-arch=x86-64 --with-tune=generic --enable-languages=c,lto,c++,fortran,ada,objc,obj-c++ --enable-shared --enable-static --enable-libatomic --enable-threads=posix --enable-graphite --enable-fully-dynamic-string --enable-libstdcxx-filesystem-ts=yes --enable-libstdcxx-time=yes --disable-libstdcxx-pch --disable-libstdcxx-debug --disable-isl-version-check --enable-lto --enable-libgomp --disable-multilib --enable-checking=release --disable-rpath --disable-win32-registry --disable-nls --disable-werror --disable-symvers --enable-plugin --with-libiconv --with-system-zlib --with-gmp=/mingw64 --with-mpfr=/mingw64 --with-mpc=/mingw64 --with-isl=/mingw64 --with-pkgversion='Rev1, Built by MSYS2 project' --with-bugurl=https://sourceforge.net/projects/msys2 --with-gnu-as --with-gnu-ld
Thread model: posix
gcc version 9.3.0 (Rev1, Built by MSYS2 project)
platform
Windows 10 Build: 18362.720
linker version
GNU ld (GNU Binutils) 2.34
mingw version
not quite sure which number is the relevant one in _mingw.h
??
build environment
I have tested using both windows command prompt and the msys-w64 shell, and
both yield the same result
MINGW64_NT-10.0-18362 3.0.7-338.x86_64 2019-07-11 10:58 UTC x86_64 Msys
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