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build: stop detecting sched_yield() on Windows

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On Windows a successful `sched_yield()` detection requires mingw-w64
built with POSIX threads (not Win32 threads) and GCC (not llvm/clang).
(linking to `winpthread` via custom options may also work.)

In CMake builds, it was pre-cached as unavailable before this patch.

When detected (via autotools), it got only used for Windows XP or older
targets combined with a non-GCC, non-clang compiler that doesn't support
`__builtin_ia32_pause()`, or with the Intel C compiler. According to
`lib/easy_lock.h`.

mingw-w64 only supports GCC and clang, leaving a very narrow chance when
`shed_yield()` gets called on Windows. Even then, `sched_yield()` is
implemented in `winpthread` as `Sleep(0)`, which may or not be a useful.
It's also trivial to implement locally if it is, and such rare build
combination is also deemed useful.

Thus, this patch marks `sched_yields()` permanently unavailable on the
Windows platform also with autotools, and instead of pre-caching, skip
this feature check with CMake.

This syncs `HAVE_SCHED_YIELDS` between builds methods on Windows.

Follow-up to 9b517c8b69a1f365fdb6f54f7153561182285b6c #11973
Follow-up to 23af112f5556d6a785c17e09f2422ac931405f61 #8680

Closes #16037
This commit is contained in:
Viktor Szakats 2025-01-16 20:39:13 +01:00
parent e49797abc2
commit 2c4bfefe91
No known key found for this signature in database
GPG Key ID: B5ABD165E2AEF201
3 changed files with 2 additions and 3 deletions
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1
CMake/win32-cache.cmake
View File

@ -131,7 +131,6 @@ set(HAVE_SEND 1)
set(HAVE_STROPTS_H 0)
set(HAVE_ARC4RANDOM 0)
set(HAVE_FNMATCH 0)
set(HAVE_SCHED_YIELD 0)
set(HAVE_ARPA_INET_H 0)
set(HAVE_FCNTL_H 1)
set(HAVE_IFADDRS_H 0)

2
CMakeLists.txt
View File

@ -1662,7 +1662,6 @@ check_symbol_exists("basename" "${CURL_INCLUDES};string.h" HAVE_BASENAME)
check_symbol_exists("opendir" "dirent.h" HAVE_OPENDIR)
check_function_exists("poll" HAVE_POLL) # poll.h
check_symbol_exists("socket" "${CURL_INCLUDES}" HAVE_SOCKET) # winsock2.h sys/socket.h
check_function_exists("sched_yield" HAVE_SCHED_YIELD)
check_symbol_exists("socketpair" "${CURL_INCLUDES}" HAVE_SOCKETPAIR) # sys/socket.h
check_symbol_exists("recv" "${CURL_INCLUDES}" HAVE_RECV) # proto/bsdsocket.h sys/types.h sys/socket.h
check_symbol_exists("send" "${CURL_INCLUDES}" HAVE_SEND) # proto/bsdsocket.h sys/types.h sys/socket.h
@ -1710,6 +1709,7 @@ check_function_exists("setmode" HAVE_SETMODE)
check_function_exists("setrlimit" HAVE_SETRLIMIT)
if(NOT WIN32)
check_function_exists("sched_yield" HAVE_SCHED_YIELD)
check_symbol_exists("strcasecmp" "string.h" HAVE_STRCASECMP)
check_symbol_exists("stricmp" "string.h" HAVE_STRICMP)
check_symbol_exists("strcmpi" "string.h" HAVE_STRCMPI)

2
configure.ac
View File

@ -4069,7 +4069,6 @@ AC_CHECK_FUNCS([\
mach_absolute_time \
pipe \
poll \
sched_yield \
sendmsg \
sendmmsg \
setlocale \
@ -4081,6 +4080,7 @@ AC_CHECK_FUNCS([\
])
if test "$curl_cv_native_windows" != 'yes'; then
AC_CHECK_FUNCS([sched_yield])
CURL_CHECK_FUNC_STRCASECMP
CURL_CHECK_FUNC_STRCMPI
CURL_CHECK_FUNC_STRICMP