From 3c64a98180148340ed72aa2c19054ddfbcfa72e1 Mon Sep 17 00:00:00 2001 From: Joseph Huber Date: Mon, 1 Jul 2024 06:30:15 -0500 Subject: [libc] Partially implement 'errno' on the GPU (#97107) Summary: The `errno` variable is expected to be `thread_local` by the standard. However, the GPU targets do not support `thread_local` and implementing that would be a large endeavor. Because of that, we previously didn't provide the `errno` symbol at all. However, to build some programs we at least need to be able to link against `errno`. Many things that would normally set `errno` completely ignore it currently (i.e. stdio) but some programs still need to be able to link against correct C programs. For this purpose this patch exports the `errno` symbol as a simple global. Internally, this will be updated atomically so it's at least not racy. Externally, this will be on the user. I've updated the documentation to state as such. This is required to get `libc++` to build. --- libc/src/errno/libc_errno.cpp | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) (limited to 'libc/src/errno/libc_errno.cpp') diff --git a/libc/src/errno/libc_errno.cpp b/libc/src/errno/libc_errno.cpp index 64f9f522ca29..bd1438c22614 100644 --- a/libc/src/errno/libc_errno.cpp +++ b/libc/src/errno/libc_errno.cpp @@ -7,16 +7,21 @@ //===----------------------------------------------------------------------===// #include "libc_errno.h" +#include "src/__support/CPP/atomic.h" #ifdef LIBC_TARGET_ARCH_IS_GPU -// LIBC_THREAD_LOCAL on GPU currently does nothing. So essentially this is just +// LIBC_THREAD_LOCAL on GPU currently does nothing. So essentially this is just // a global errno for gpu to use for now. extern "C" { -LIBC_THREAD_LOCAL int __llvmlibc_gpu_errno; +LIBC_THREAD_LOCAL LIBC_NAMESPACE::cpp::Atomic __llvmlibc_errno; } -void LIBC_NAMESPACE::Errno::operator=(int a) { __llvmlibc_gpu_errno = a; } -LIBC_NAMESPACE::Errno::operator int() { return __llvmlibc_gpu_errno; } +void LIBC_NAMESPACE::Errno::operator=(int a) { + __llvmlibc_errno.store(a, cpp::MemoryOrder::RELAXED); +} +LIBC_NAMESPACE::Errno::operator int() { + return __llvmlibc_errno.load(cpp::MemoryOrder::RELAXED); +} #elif !defined(LIBC_COPT_PUBLIC_PACKAGING) // This mode is for unit testing. We just use our internal errno. -- cgit v1.2.3