From e6cdbfaa3341fd1768fd95d8136aad0de6956e8b Mon Sep 17 00:00:00 2001 From: Matthew Fernandez Date: Tue, 9 Dec 2025 11:10:41 -0800 Subject: [PATCH] common: make 'emit_once' thread safe MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit By using a global in a thread-unsafe way, this logic was a barrier to introducing multi-threading here in future. Rather than trying complicated modifications to the logic, this change just introduces a lock around `emit_once`, assuming blocking while another thread runs this function is acceptable. This is the first introduction of C++/C11/POSIX threading in the code base. Although C11 threads are an optional feature and POSIX threads are not guaranteed available, there are no known supported platforms lacking both. It is assumed at least one of these is usable: ┌──────────────────┬──────────────────┬────────────────────┐ │ operating system │ has C11 threads? │ has POSIX threads? │ ├──────────────────┼──────────────────┼────────────────────┤ │ Cygwin │ yes │ yes │ │ Linux │ yes │ yes │ │ macOS │ │ yes │ │ MinGW │ │ yes │ │ Windows │ yes │ │ └──────────────────┴──────────────────┴────────────────────┘ A wrinkle to this is that it was discovered that `cpack` crashes on 32-bit Windows in a Debug build when linking against C11 threads. The cause of this is unknown at time of writing, but rather than debug this C++ threads have been used on Windows instead. MSVC is guaranteed to be able to build and link C++ as well as C. It is assumed that unconditionally using C++ threads would be undesirable because, despite their universal availability, linking against C++’s standard library is sometimes unwanted in Unix ecosystems. The Autotools support follows the advice in the `AX_PTHREAD` docs for enabling POSIX threads project-wide.¹ So, as odd as it looks, it is not a typo e.g. appending `$PTHREAD_CFLAGS` to `$CXXFLAGS`. `emit_once_reset` remains thread-unsafe. ¹ https://www.gnu.org/software/autoconf-archive/ax_pthread.html Gitlab: #2558, #2719 --- CHANGELOG.md | 3 + CMakeLists.txt | 11 + configure.ac | 14 ++ lib/common/emit.c | 12 + lib/util/CMakeLists.txt | 11 + lib/util/Makefile.am | 11 +- lib/util/mutex-c11.c | 43 ++++ lib/util/mutex-cxx.cc | 31 +++ lib/util/mutex-pthread.c | 43 ++++ lib/util/mutex.h | 93 +++++++ m4/README | 4 + m4/ax_pthread.m4 | 522 +++++++++++++++++++++++++++++++++++++++ 12 files changed, 796 insertions(+), 2 deletions(-) create mode 100644 lib/util/mutex-c11.c create mode 100644 lib/util/mutex-cxx.cc create mode 100644 lib/util/mutex-pthread.c create mode 100644 lib/util/mutex.h create mode 100644 m4/ax_pthread.m4 diff --git a/CHANGELOG.md b/CHANGELOG.md index 87402b310b..2c89ce1dfa 100644 --- a/CHANGELOG.md +++ b/CHANGELOG.md @@ -11,6 +11,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0 - When seeding random number generators with `time(NULL)`, the result of `getpid()` is no longer also mixed in. Previously this was the case on non-Windows platforms, impeding reproducibility and portability. +- Graphviz libraries and programs depend on a threading library, either C11 + threads, C++ threads, or POSIX threads. If both C11 threads and POSIX threads + are available during compilation, the default selected is POSIX threads. ### Fixed diff --git a/CMakeLists.txt b/CMakeLists.txt index b02632b1f5..f33d75d5dd 100644 --- a/CMakeLists.txt +++ b/CMakeLists.txt @@ -790,6 +790,17 @@ if(${CMAKE_CXX_COMPILER_ID} STREQUAL MSVC) set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /experimental:c11atomics") endif() +if(${CMAKE_CXX_COMPILER_ID} STREQUAL MSVC) + message(STATUS "using C++11 threads") +else() + find_package(Threads REQUIRED) + if(CMAKE_USE_PTHREADS_INIT) + message(STATUS "using POSIX threads") + else() + message(STATUS "using C11 threads") + endif() +endif() + set(CMAKE_POSITION_INDEPENDENT_CODE ON) # enable LTO in release builds diff --git a/configure.ac b/configure.ac index 073124276f..6ebf4d4679 100644 --- a/configure.ac +++ b/configure.ac @@ -283,6 +283,19 @@ AC_PROG_CXX AX_CXX_COMPILE_STDCXX_17(noext,mandatory) AC_PROG_OBJC +# enable POSIX threads or fallback to C11 threads +AX_PTHREAD([ + LIBS="$PTHREAD_LIBS $LIBS" + CFLAGS+=" $PTHREAD_CFLAGS" + CXXFLAGS+=" $PTHREAD_CFLAGS" + CC="$PTHREAD_CC" + CXX="$PTHREAD_CXX" + use_pthread="Yes" +],[ + use_pthread="No (falling back to C11 threads)" +]) +AM_CONDITIONAL(WITH_PTHREAD, [test "$use_pthread" = "Yes"]) + dnl =========================================================================== dnl Set GCC compiler flags @@ -2195,6 +2208,7 @@ echo " gts: $use_gts" echo " ipsepcola: $use_ipsepcola" echo " ltdl: $use_ltdl" echo " ortho: $use_ortho" +echo " pthreads: $use_pthread" echo " sfdp: $use_sfdp" echo " swig: $use_swig ( $SWIG_VERSION )" echo " shared: $use_shared" diff --git a/lib/common/emit.c b/lib/common/emit.c index 062439acbe..4099a9f29b 100644 --- a/lib/common/emit.c +++ b/lib/common/emit.c @@ -38,6 +38,7 @@ #include #include #include +#include #include #include #include @@ -3719,6 +3720,7 @@ void emit_graph(GVJ_t * job, graph_t * g) emit_end_graph(job); } +static mutex_t *_Atomic strings_lock; static Dict_t *strings; static Dtdisc_t stringdict = { .link = -1, // link - allocate separate holder objects @@ -3726,12 +3728,17 @@ static Dtdisc_t stringdict = { }; bool emit_once(char *str) { + mutex_lazy_init_or_die(&strings_lock); + + gv_mutex_lock(strings_lock); if (strings == 0) strings = dtopen(&stringdict, Dtoset); if (!dtsearch(strings, str)) { dtinsert(strings, gv_strdup(str)); + gv_mutex_unlock(strings_lock); return true; } + gv_mutex_unlock(strings_lock); return false; } @@ -3740,6 +3747,11 @@ void emit_once_reset(void) if (strings) { dtclose(strings); strings = 0; + + if (strings_lock != NULL) { + gv_mutex_free(strings_lock); + } + strings_lock = NULL; } } diff --git a/lib/util/CMakeLists.txt b/lib/util/CMakeLists.txt index 04344ed5db..b9471b27e9 100644 --- a/lib/util/CMakeLists.txt +++ b/lib/util/CMakeLists.txt @@ -10,6 +10,17 @@ add_library(util STATIC target_include_directories(util PRIVATE ..) +if(${CMAKE_CXX_COMPILER_ID} STREQUAL MSVC) + target_sources(util PRIVATE mutex-cxx.cc) +else() + if(CMAKE_USE_PTHREADS_INIT) + target_sources(util PRIVATE mutex-pthread.c) + else() + target_sources(util PRIVATE mutex-c11.c) + endif() + target_link_libraries(util PRIVATE Threads::Threads) +endif() + if(WIN32 AND NOT MINGW) target_include_directories(util PRIVATE ../../windows/include/unistd) endif() diff --git a/lib/util/Makefile.am b/lib/util/Makefile.am index 9212a96116..20dbb7e35c 100644 --- a/lib/util/Makefile.am +++ b/lib/util/Makefile.am @@ -19,6 +19,7 @@ noinst_HEADERS = \ list.h \ list-private.h \ lockfile.h \ + mutex.h \ optional.h \ overflow.h \ path.h \ @@ -35,8 +36,14 @@ noinst_HEADERS = \ xml.h noinst_LTLIBRARIES = libutil_C.la +if WITH_PTHREAD +MUTEX=mutex-pthread.c +else +MUTEX=mutex-c11.c +endif + libutil_C_la_SOURCES = arena.c base64.c gv_find_me.c gv_fopen.c list.c \ - random.c xml.c + $(MUTEX) random.c xml.c libutil_C_la_CPPFLAGS = $(AM_CPPFLAGS) -EXTRA_DIST = README +EXTRA_DIST = mutex-cxx.cc README diff --git a/lib/util/mutex-c11.c b/lib/util/mutex-c11.c new file mode 100644 index 0000000000..97cba33840 --- /dev/null +++ b/lib/util/mutex-c11.c @@ -0,0 +1,43 @@ +/// @file +/// @brief Implementation of mutex.h backed by C11 threads + +#include +#include +#include +#include + +struct mutex { + mtx_t impl; +}; + +mutex_t *gv_mutex_new(void) { + mutex_t *const m = calloc(1, sizeof(*m)); + if (m == NULL) { + return NULL; + } + if (mtx_init(&m->impl, mtx_plain) != thrd_success) { + free(m); + return NULL; + } + return m; +} + +void gv_mutex_lock(mutex_t *m) { + assert(m != NULL); + const int r = mtx_lock(&m->impl); + assert(r == thrd_success); + (void)r; +} + +void gv_mutex_unlock(mutex_t *m) { + assert(m != NULL); + const int r = mtx_unlock(&m->impl); + assert(r == thrd_success); + (void)r; +} + +void gv_mutex_free(mutex_t *m) { + assert(m != NULL); + mtx_destroy(&m->impl); + free(m); +} diff --git a/lib/util/mutex-cxx.cc b/lib/util/mutex-cxx.cc new file mode 100644 index 0000000000..63b16e54e2 --- /dev/null +++ b/lib/util/mutex-cxx.cc @@ -0,0 +1,31 @@ +/// @file +/// @brief Implementation of mutex.h backed by C++11 `std::mutex` + +#include +#include +#include +#include + +struct mutex { + std::mutex impl; +}; + +mutex_t *gv_mutex_new(void) { + try { + return new mutex; + } catch (std::bad_alloc &) { + return nullptr; + } +} + +void gv_mutex_lock(mutex_t *m) { + assert(m != nullptr); + m->impl.lock(); +} + +void gv_mutex_unlock(mutex_t *m) { + assert(m != nullptr); + m->impl.unlock(); +} + +void gv_mutex_free(mutex_t *m) { delete m; } diff --git a/lib/util/mutex-pthread.c b/lib/util/mutex-pthread.c new file mode 100644 index 0000000000..a48ace63b0 --- /dev/null +++ b/lib/util/mutex-pthread.c @@ -0,0 +1,43 @@ +/// @file +/// @brief Implementation of mutex.h backed by POSIX threads + +#include +#include +#include +#include + +struct mutex { + pthread_mutex_t impl; +}; + +mutex_t *gv_mutex_new(void) { + mutex_t *const m = calloc(1, sizeof(*m)); + if (m == NULL) { + return NULL; + } + if (pthread_mutex_init(&m->impl, NULL) != 0) { + free(m); + return NULL; + } + return m; +} + +void gv_mutex_lock(mutex_t *m) { + assert(m != NULL); + const int r = pthread_mutex_lock(&m->impl); + assert(r == 0); + (void)r; +} + +void gv_mutex_unlock(mutex_t *m) { + assert(m != NULL); + const int r = pthread_mutex_unlock(&m->impl); + assert(r == 0); + (void)r; +} + +void gv_mutex_free(mutex_t *m) { + assert(m != NULL); + (void)pthread_mutex_destroy(&m->impl); + free(m); +} diff --git a/lib/util/mutex.h b/lib/util/mutex.h new file mode 100644 index 0000000000..2428a93854 --- /dev/null +++ b/lib/util/mutex.h @@ -0,0 +1,93 @@ +/// @file +/// @brief Platform abstraction for mutex locks + +#pragma once + +#include +#include +#include +#include +#include + +/// opaque type of a mutex +typedef struct mutex mutex_t; + +#ifdef __cplusplus +extern "C" { +#endif + +/// create a new mutex +/// +/// @return Created mutex on success or `NULL` on failure +UTIL_API mutex_t *gv_mutex_new(void); + +/// acquire a mutex +UTIL_API void gv_mutex_lock(mutex_t *m); + +/// release a mutex +/// +/// Behavior is undefined if the caller does not hold the given mutex. +UTIL_API void gv_mutex_unlock(mutex_t *m); + +/// deallocate resources associated with a mutex +UTIL_API void gv_mutex_free(mutex_t *m); + +#ifdef __cplusplus +} +#endif + +#ifndef __cplusplus + +// `_Atomic` is a keyword in C, but not available at all in C++ + +/// `gv_mutex_new` for multi-threaded situations +/// +/// Sometimes there is no safe known-single-threaded context in which to +/// initialize a mutex. POSIX threads has `PTHREAD_MUTEX_INITIALIZER` for this, +/// but there is not a good platform-independent answer to this problem. This +/// function offers something that can be safely called repeatedly from a +/// possibly multi-threaded context to initialize a pointer to a mutex. This +/// should be avoided if it is possible to call `gv_mutex_new` instead. +/// +/// @param mptr [inout] Mutex pointer to initialize +/// @return 0 on success +static inline int mutex_lazy_init(mutex_t *_Atomic *mptr) { + + // is the mutex already initialized? + mutex_t *m = atomic_load_explicit(mptr, memory_order_acquire); +retry: + if (m != NULL) { + return 0; + } + + // create a new mutex + mutex_t *const attempt = gv_mutex_new(); + if (attempt == NULL) { + return -1; + } + + // make this globally visible + if (!atomic_compare_exchange_strong_explicit( + mptr, &m, attempt, memory_order_acq_rel, memory_order_acquire)) { + // failed because we raced with another thread; retry + gv_mutex_free(attempt); + goto retry; + } + + return 0; +} + +/// `mutex_lazy_init`, exiting on failure +static inline void mutex_lazy_init_or_die(mutex_t *_Atomic *mptr) { + assert(mptr != NULL); + const int r = mutex_lazy_init(mptr); + if (r != 0) { + fputs("mutex_lazy_init failed\n", stderr); + graphviz_exit(EXIT_FAILURE); + } +} + +#endif diff --git a/m4/README b/m4/README index d30dd0424a..ff35611756 100644 --- a/m4/README +++ b/m4/README @@ -5,3 +5,7 @@ The file ax_check_compile_flag.m4 was obtained from commit The files ax_cxx_compile_stdcxx.m4 and ax_cxx_compile_stdcxx_11.m4 were obtained from commit efa6f204a6124e882abbbc6e056c91edfdc30555 of https://git.savannah.gnu.org/git/autoconf-archive.git + +The file ax_pthread.m4 was obtained from commit +dcff834afae34861f7f11f3d51e0c938a35bd30f of + https://git.savannah.gnu.org/git/autoconf-archive.git diff --git a/m4/ax_pthread.m4 b/m4/ax_pthread.m4 new file mode 100644 index 0000000000..9f35d13914 --- /dev/null +++ b/m4/ax_pthread.m4 @@ -0,0 +1,522 @@ +# =========================================================================== +# https://www.gnu.org/software/autoconf-archive/ax_pthread.html +# =========================================================================== +# +# SYNOPSIS +# +# AX_PTHREAD([ACTION-IF-FOUND[, ACTION-IF-NOT-FOUND]]) +# +# DESCRIPTION +# +# This macro figures out how to build C programs using POSIX threads. It +# sets the PTHREAD_LIBS output variable to the threads library and linker +# flags, and the PTHREAD_CFLAGS output variable to any special C compiler +# flags that are needed. (The user can also force certain compiler +# flags/libs to be tested by setting these environment variables.) +# +# Also sets PTHREAD_CC and PTHREAD_CXX to any special C compiler that is +# needed for multi-threaded programs (defaults to the value of CC +# respectively CXX otherwise). (This is necessary on e.g. AIX to use the +# special cc_r/CC_r compiler alias.) +# +# NOTE: You are assumed to not only compile your program with these flags, +# but also to link with them as well. For example, you might link with +# $PTHREAD_CC $CFLAGS $PTHREAD_CFLAGS $LDFLAGS ... $PTHREAD_LIBS $LIBS +# $PTHREAD_CXX $CXXFLAGS $PTHREAD_CFLAGS $LDFLAGS ... $PTHREAD_LIBS $LIBS +# +# If you are only building threaded programs, you may wish to use these +# variables in your default LIBS, CFLAGS, and CC: +# +# LIBS="$PTHREAD_LIBS $LIBS" +# CFLAGS="$CFLAGS $PTHREAD_CFLAGS" +# CXXFLAGS="$CXXFLAGS $PTHREAD_CFLAGS" +# CC="$PTHREAD_CC" +# CXX="$PTHREAD_CXX" +# +# In addition, if the PTHREAD_CREATE_JOINABLE thread-attribute constant +# has a nonstandard name, this macro defines PTHREAD_CREATE_JOINABLE to +# that name (e.g. PTHREAD_CREATE_UNDETACHED on AIX). +# +# Also HAVE_PTHREAD_PRIO_INHERIT is defined if pthread is found and the +# PTHREAD_PRIO_INHERIT symbol is defined when compiling with +# PTHREAD_CFLAGS. +# +# ACTION-IF-FOUND is a list of shell commands to run if a threads library +# is found, and ACTION-IF-NOT-FOUND is a list of commands to run it if it +# is not found. If ACTION-IF-FOUND is not specified, the default action +# will define HAVE_PTHREAD. +# +# Please let the authors know if this macro fails on any platform, or if +# you have any other suggestions or comments. This macro was based on work +# by SGJ on autoconf scripts for FFTW (http://www.fftw.org/) (with help +# from M. Frigo), as well as ac_pthread and hb_pthread macros posted by +# Alejandro Forero Cuervo to the autoconf macro repository. We are also +# grateful for the helpful feedback of numerous users. +# +# Updated for Autoconf 2.68 by Daniel Richard G. +# +# LICENSE +# +# Copyright (c) 2008 Steven G. Johnson +# Copyright (c) 2011 Daniel Richard G. +# Copyright (c) 2019 Marc Stevens +# +# This program is free software: you can redistribute it and/or modify it +# under the terms of the GNU General Public License as published by the +# Free Software Foundation, either version 3 of the License, or (at your +# option) any later version. +# +# This program is distributed in the hope that it will be useful, but +# WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General +# Public License for more details. +# +# You should have received a copy of the GNU General Public License along +# with this program. If not, see . +# +# As a special exception, the respective Autoconf Macro's copyright owner +# gives unlimited permission to copy, distribute and modify the configure +# scripts that are the output of Autoconf when processing the Macro. You +# need not follow the terms of the GNU General Public License when using +# or distributing such scripts, even though portions of the text of the +# Macro appear in them. The GNU General Public License (GPL) does govern +# all other use of the material that constitutes the Autoconf Macro. +# +# This special exception to the GPL applies to versions of the Autoconf +# Macro released by the Autoconf Archive. When you make and distribute a +# modified version of the Autoconf Macro, you may extend this special +# exception to the GPL to apply to your modified version as well. + +#serial 31 + +AU_ALIAS([ACX_PTHREAD], [AX_PTHREAD]) +AC_DEFUN([AX_PTHREAD], [ +AC_REQUIRE([AC_CANONICAL_HOST]) +AC_REQUIRE([AC_PROG_CC]) +AC_REQUIRE([AC_PROG_SED]) +AC_LANG_PUSH([C]) +ax_pthread_ok=no + +# We used to check for pthread.h first, but this fails if pthread.h +# requires special compiler flags (e.g. on Tru64 or Sequent). +# It gets checked for in the link test anyway. + +# First of all, check if the user has set any of the PTHREAD_LIBS, +# etcetera environment variables, and if threads linking works using +# them: +if test "x$PTHREAD_CFLAGS$PTHREAD_LIBS" != "x"; then + ax_pthread_save_CC="$CC" + ax_pthread_save_CFLAGS="$CFLAGS" + ax_pthread_save_LIBS="$LIBS" + AS_IF([test "x$PTHREAD_CC" != "x"], [CC="$PTHREAD_CC"]) + AS_IF([test "x$PTHREAD_CXX" != "x"], [CXX="$PTHREAD_CXX"]) + CFLAGS="$CFLAGS $PTHREAD_CFLAGS" + LIBS="$PTHREAD_LIBS $LIBS" + AC_MSG_CHECKING([for pthread_join using $CC $PTHREAD_CFLAGS $PTHREAD_LIBS]) + AC_LINK_IFELSE([AC_LANG_CALL([], [pthread_join])], [ax_pthread_ok=yes]) + AC_MSG_RESULT([$ax_pthread_ok]) + if test "x$ax_pthread_ok" = "xno"; then + PTHREAD_LIBS="" + PTHREAD_CFLAGS="" + fi + CC="$ax_pthread_save_CC" + CFLAGS="$ax_pthread_save_CFLAGS" + LIBS="$ax_pthread_save_LIBS" +fi + +# We must check for the threads library under a number of different +# names; the ordering is very important because some systems +# (e.g. DEC) have both -lpthread and -lpthreads, where one of the +# libraries is broken (non-POSIX). + +# Create a list of thread flags to try. Items with a "," contain both +# C compiler flags (before ",") and linker flags (after ","). Other items +# starting with a "-" are C compiler flags, and remaining items are +# library names, except for "none" which indicates that we try without +# any flags at all, and "pthread-config" which is a program returning +# the flags for the Pth emulation library. + +ax_pthread_flags="pthreads none -Kthread -pthread -pthreads -mthreads pthread --thread-safe -mt pthread-config" + +# The ordering *is* (sometimes) important. Some notes on the +# individual items follow: + +# pthreads: AIX (must check this before -lpthread) +# none: in case threads are in libc; should be tried before -Kthread and +# other compiler flags to prevent continual compiler warnings +# -Kthread: Sequent (threads in libc, but -Kthread needed for pthread.h) +# -pthread: Linux/gcc (kernel threads), BSD/gcc (userland threads), Tru64 +# (Note: HP C rejects this with "bad form for `-t' option") +# -pthreads: Solaris/gcc (Note: HP C also rejects) +# -mt: Sun Workshop C (may only link SunOS threads [-lthread], but it +# doesn't hurt to check since this sometimes defines pthreads and +# -D_REENTRANT too), HP C (must be checked before -lpthread, which +# is present but should not be used directly; and before -mthreads, +# because the compiler interprets this as "-mt" + "-hreads") +# -mthreads: Mingw32/gcc, Lynx/gcc +# pthread: Linux, etcetera +# --thread-safe: KAI C++ +# pthread-config: use pthread-config program (for GNU Pth library) + +case $host_os in + + freebsd*) + + # -kthread: FreeBSD kernel threads (preferred to -pthread since SMP-able) + # lthread: LinuxThreads port on FreeBSD (also preferred to -pthread) + + ax_pthread_flags="-kthread lthread $ax_pthread_flags" + ;; + + hpux*) + + # From the cc(1) man page: "[-mt] Sets various -D flags to enable + # multi-threading and also sets -lpthread." + + ax_pthread_flags="-mt -pthread pthread $ax_pthread_flags" + ;; + + openedition*) + + # IBM z/OS requires a feature-test macro to be defined in order to + # enable POSIX threads at all, so give the user a hint if this is + # not set. (We don't define these ourselves, as they can affect + # other portions of the system API in unpredictable ways.) + + AC_EGREP_CPP([AX_PTHREAD_ZOS_MISSING], + [ +# if !defined(_OPEN_THREADS) && !defined(_UNIX03_THREADS) + AX_PTHREAD_ZOS_MISSING +# endif + ], + [AC_MSG_WARN([IBM z/OS requires -D_OPEN_THREADS or -D_UNIX03_THREADS to enable pthreads support.])]) + ;; + + solaris*) + + # On Solaris (at least, for some versions), libc contains stubbed + # (non-functional) versions of the pthreads routines, so link-based + # tests will erroneously succeed. (N.B.: The stubs are missing + # pthread_cleanup_push, or rather a function called by this macro, + # so we could check for that, but who knows whether they'll stub + # that too in a future libc.) So we'll check first for the + # standard Solaris way of linking pthreads (-mt -lpthread). + + ax_pthread_flags="-mt,-lpthread pthread $ax_pthread_flags" + ;; +esac + +# Are we compiling with Clang? + +AC_CACHE_CHECK([whether $CC is Clang], + [ax_cv_PTHREAD_CLANG], + [ax_cv_PTHREAD_CLANG=no + # Note that Autoconf sets GCC=yes for Clang as well as GCC + if test "x$GCC" = "xyes"; then + AC_EGREP_CPP([AX_PTHREAD_CC_IS_CLANG], + [/* Note: Clang 2.7 lacks __clang_[a-z]+__ */ +# if defined(__clang__) && defined(__llvm__) + AX_PTHREAD_CC_IS_CLANG +# endif + ], + [ax_cv_PTHREAD_CLANG=yes]) + fi + ]) +ax_pthread_clang="$ax_cv_PTHREAD_CLANG" + + +# GCC generally uses -pthread, or -pthreads on some platforms (e.g. SPARC) + +# Note that for GCC and Clang -pthread generally implies -lpthread, +# except when -nostdlib is passed. +# This is problematic using libtool to build C++ shared libraries with pthread: +# [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=25460 +# [2] https://bugzilla.redhat.com/show_bug.cgi?id=661333 +# [3] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=468555 +# To solve this, first try -pthread together with -lpthread for GCC + +AS_IF([test "x$GCC" = "xyes"], + [ax_pthread_flags="-pthread,-lpthread -pthread -pthreads $ax_pthread_flags"]) + +# Clang takes -pthread (never supported any other flag), but we'll try with -lpthread first + +AS_IF([test "x$ax_pthread_clang" = "xyes"], + [ax_pthread_flags="-pthread,-lpthread -pthread"]) + + +# The presence of a feature test macro requesting re-entrant function +# definitions is, on some systems, a strong hint that pthreads support is +# correctly enabled + +case $host_os in + darwin* | hpux* | linux* | osf* | solaris*) + ax_pthread_check_macro="_REENTRANT" + ;; + + aix*) + ax_pthread_check_macro="_THREAD_SAFE" + ;; + + *) + ax_pthread_check_macro="--" + ;; +esac +AS_IF([test "x$ax_pthread_check_macro" = "x--"], + [ax_pthread_check_cond=0], + [ax_pthread_check_cond="!defined($ax_pthread_check_macro)"]) + + +if test "x$ax_pthread_ok" = "xno"; then +for ax_pthread_try_flag in $ax_pthread_flags; do + + case $ax_pthread_try_flag in + none) + AC_MSG_CHECKING([whether pthreads work without any flags]) + ;; + + *,*) + PTHREAD_CFLAGS=`echo $ax_pthread_try_flag | sed "s/^\(.*\),\(.*\)$/\1/"` + PTHREAD_LIBS=`echo $ax_pthread_try_flag | sed "s/^\(.*\),\(.*\)$/\2/"` + AC_MSG_CHECKING([whether pthreads work with "$PTHREAD_CFLAGS" and "$PTHREAD_LIBS"]) + ;; + + -*) + AC_MSG_CHECKING([whether pthreads work with $ax_pthread_try_flag]) + PTHREAD_CFLAGS="$ax_pthread_try_flag" + ;; + + pthread-config) + AC_CHECK_PROG([ax_pthread_config], [pthread-config], [yes], [no]) + AS_IF([test "x$ax_pthread_config" = "xno"], [continue]) + PTHREAD_CFLAGS="`pthread-config --cflags`" + PTHREAD_LIBS="`pthread-config --ldflags` `pthread-config --libs`" + ;; + + *) + AC_MSG_CHECKING([for the pthreads library -l$ax_pthread_try_flag]) + PTHREAD_LIBS="-l$ax_pthread_try_flag" + ;; + esac + + ax_pthread_save_CFLAGS="$CFLAGS" + ax_pthread_save_LIBS="$LIBS" + CFLAGS="$CFLAGS $PTHREAD_CFLAGS" + LIBS="$PTHREAD_LIBS $LIBS" + + # Check for various functions. We must include pthread.h, + # since some functions may be macros. (On the Sequent, we + # need a special flag -Kthread to make this header compile.) + # We check for pthread_join because it is in -lpthread on IRIX + # while pthread_create is in libc. We check for pthread_attr_init + # due to DEC craziness with -lpthreads. We check for + # pthread_cleanup_push because it is one of the few pthread + # functions on Solaris that doesn't have a non-functional libc stub. + # We try pthread_create on general principles. + + AC_LINK_IFELSE([AC_LANG_PROGRAM([#include +# if $ax_pthread_check_cond +# error "$ax_pthread_check_macro must be defined" +# endif + static void *some_global = NULL; + static void routine(void *a) + { + /* To avoid any unused-parameter or + unused-but-set-parameter warning. */ + some_global = a; + } + static void *start_routine(void *a) { return a; }], + [pthread_t th; pthread_attr_t attr; + pthread_create(&th, 0, start_routine, 0); + pthread_join(th, 0); + pthread_attr_init(&attr); + pthread_cleanup_push(routine, 0); + pthread_cleanup_pop(0) /* ; */])], + [ax_pthread_ok=yes], + []) + + CFLAGS="$ax_pthread_save_CFLAGS" + LIBS="$ax_pthread_save_LIBS" + + AC_MSG_RESULT([$ax_pthread_ok]) + AS_IF([test "x$ax_pthread_ok" = "xyes"], [break]) + + PTHREAD_LIBS="" + PTHREAD_CFLAGS="" +done +fi + + +# Clang needs special handling, because older versions handle the -pthread +# option in a rather... idiosyncratic way + +if test "x$ax_pthread_clang" = "xyes"; then + + # Clang takes -pthread; it has never supported any other flag + + # (Note 1: This will need to be revisited if a system that Clang + # supports has POSIX threads in a separate library. This tends not + # to be the way of modern systems, but it's conceivable.) + + # (Note 2: On some systems, notably Darwin, -pthread is not needed + # to get POSIX threads support; the API is always present and + # active. We could reasonably leave PTHREAD_CFLAGS empty. But + # -pthread does define _REENTRANT, and while the Darwin headers + # ignore this macro, third-party headers might not.) + + # However, older versions of Clang make a point of warning the user + # that, in an invocation where only linking and no compilation is + # taking place, the -pthread option has no effect ("argument unused + # during compilation"). They expect -pthread to be passed in only + # when source code is being compiled. + # + # Problem is, this is at odds with the way Automake and most other + # C build frameworks function, which is that the same flags used in + # compilation (CFLAGS) are also used in linking. Many systems + # supported by AX_PTHREAD require exactly this for POSIX threads + # support, and in fact it is often not straightforward to specify a + # flag that is used only in the compilation phase and not in + # linking. Such a scenario is extremely rare in practice. + # + # Even though use of the -pthread flag in linking would only print + # a warning, this can be a nuisance for well-run software projects + # that build with -Werror. So if the active version of Clang has + # this misfeature, we search for an option to squash it. + + AC_CACHE_CHECK([whether Clang needs flag to prevent "argument unused" warning when linking with -pthread], + [ax_cv_PTHREAD_CLANG_NO_WARN_FLAG], + [ax_cv_PTHREAD_CLANG_NO_WARN_FLAG=unknown + # Create an alternate version of $ac_link that compiles and + # links in two steps (.c -> .o, .o -> exe) instead of one + # (.c -> exe), because the warning occurs only in the second + # step + ax_pthread_save_ac_link="$ac_link" + ax_pthread_sed='s/conftest\.\$ac_ext/conftest.$ac_objext/g' + ax_pthread_link_step=`AS_ECHO(["$ac_link"]) | sed "$ax_pthread_sed"` + ax_pthread_2step_ac_link="($ac_compile) && (echo ==== >&5) && ($ax_pthread_link_step)" + ax_pthread_save_CFLAGS="$CFLAGS" + for ax_pthread_try in '' -Qunused-arguments -Wno-unused-command-line-argument unknown; do + AS_IF([test "x$ax_pthread_try" = "xunknown"], [break]) + CFLAGS="-Werror -Wunknown-warning-option $ax_pthread_try -pthread $ax_pthread_save_CFLAGS" + ac_link="$ax_pthread_save_ac_link" + AC_LINK_IFELSE([AC_LANG_SOURCE([[int main(void){return 0;}]])], + [ac_link="$ax_pthread_2step_ac_link" + AC_LINK_IFELSE([AC_LANG_SOURCE([[int main(void){return 0;}]])], + [break]) + ]) + done + ac_link="$ax_pthread_save_ac_link" + CFLAGS="$ax_pthread_save_CFLAGS" + AS_IF([test "x$ax_pthread_try" = "x"], [ax_pthread_try=no]) + ax_cv_PTHREAD_CLANG_NO_WARN_FLAG="$ax_pthread_try" + ]) + + case "$ax_cv_PTHREAD_CLANG_NO_WARN_FLAG" in + no | unknown) ;; + *) PTHREAD_CFLAGS="$ax_cv_PTHREAD_CLANG_NO_WARN_FLAG $PTHREAD_CFLAGS" ;; + esac + +fi # $ax_pthread_clang = yes + + + +# Various other checks: +if test "x$ax_pthread_ok" = "xyes"; then + ax_pthread_save_CFLAGS="$CFLAGS" + ax_pthread_save_LIBS="$LIBS" + CFLAGS="$CFLAGS $PTHREAD_CFLAGS" + LIBS="$PTHREAD_LIBS $LIBS" + + # Detect AIX lossage: JOINABLE attribute is called UNDETACHED. + AC_CACHE_CHECK([for joinable pthread attribute], + [ax_cv_PTHREAD_JOINABLE_ATTR], + [ax_cv_PTHREAD_JOINABLE_ATTR=unknown + for ax_pthread_attr in PTHREAD_CREATE_JOINABLE PTHREAD_CREATE_UNDETACHED; do + AC_LINK_IFELSE([AC_LANG_PROGRAM([#include ], + [int attr = $ax_pthread_attr; return attr /* ; */])], + [ax_cv_PTHREAD_JOINABLE_ATTR=$ax_pthread_attr; break], + []) + done + ]) + AS_IF([test "x$ax_cv_PTHREAD_JOINABLE_ATTR" != "xunknown" && \ + test "x$ax_cv_PTHREAD_JOINABLE_ATTR" != "xPTHREAD_CREATE_JOINABLE" && \ + test "x$ax_pthread_joinable_attr_defined" != "xyes"], + [AC_DEFINE_UNQUOTED([PTHREAD_CREATE_JOINABLE], + [$ax_cv_PTHREAD_JOINABLE_ATTR], + [Define to necessary symbol if this constant + uses a non-standard name on your system.]) + ax_pthread_joinable_attr_defined=yes + ]) + + AC_CACHE_CHECK([whether more special flags are required for pthreads], + [ax_cv_PTHREAD_SPECIAL_FLAGS], + [ax_cv_PTHREAD_SPECIAL_FLAGS=no + case $host_os in + solaris*) + ax_cv_PTHREAD_SPECIAL_FLAGS="-D_POSIX_PTHREAD_SEMANTICS" + ;; + esac + ]) + AS_IF([test "x$ax_cv_PTHREAD_SPECIAL_FLAGS" != "xno" && \ + test "x$ax_pthread_special_flags_added" != "xyes"], + [PTHREAD_CFLAGS="$ax_cv_PTHREAD_SPECIAL_FLAGS $PTHREAD_CFLAGS" + ax_pthread_special_flags_added=yes]) + + AC_CACHE_CHECK([for PTHREAD_PRIO_INHERIT], + [ax_cv_PTHREAD_PRIO_INHERIT], + [AC_LINK_IFELSE([AC_LANG_PROGRAM([[#include ]], + [[int i = PTHREAD_PRIO_INHERIT; + return i;]])], + [ax_cv_PTHREAD_PRIO_INHERIT=yes], + [ax_cv_PTHREAD_PRIO_INHERIT=no]) + ]) + AS_IF([test "x$ax_cv_PTHREAD_PRIO_INHERIT" = "xyes" && \ + test "x$ax_pthread_prio_inherit_defined" != "xyes"], + [AC_DEFINE([HAVE_PTHREAD_PRIO_INHERIT], [1], [Have PTHREAD_PRIO_INHERIT.]) + ax_pthread_prio_inherit_defined=yes + ]) + + CFLAGS="$ax_pthread_save_CFLAGS" + LIBS="$ax_pthread_save_LIBS" + + # More AIX lossage: compile with *_r variant + if test "x$GCC" != "xyes"; then + case $host_os in + aix*) + AS_CASE(["x/$CC"], + [x*/c89|x*/c89_128|x*/c99|x*/c99_128|x*/cc|x*/cc128|x*/xlc|x*/xlc_v6|x*/xlc128|x*/xlc128_v6], + [#handle absolute path differently from PATH based program lookup + AS_CASE(["x$CC"], + [x/*], + [ + AS_IF([AS_EXECUTABLE_P([${CC}_r])],[PTHREAD_CC="${CC}_r"]) + AS_IF([test "x${CXX}" != "x"], [AS_IF([AS_EXECUTABLE_P([${CXX}_r])],[PTHREAD_CXX="${CXX}_r"])]) + ], + [ + AC_CHECK_PROGS([PTHREAD_CC],[${CC}_r],[$CC]) + AS_IF([test "x${CXX}" != "x"], [AC_CHECK_PROGS([PTHREAD_CXX],[${CXX}_r],[$CXX])]) + ] + ) + ]) + ;; + esac + fi +fi + +test -n "$PTHREAD_CC" || PTHREAD_CC="$CC" +test -n "$PTHREAD_CXX" || PTHREAD_CXX="$CXX" + +AC_SUBST([PTHREAD_LIBS]) +AC_SUBST([PTHREAD_CFLAGS]) +AC_SUBST([PTHREAD_CC]) +AC_SUBST([PTHREAD_CXX]) + +# Finally, execute ACTION-IF-FOUND/ACTION-IF-NOT-FOUND: +if test "x$ax_pthread_ok" = "xyes"; then + ifelse([$1],,[AC_DEFINE([HAVE_PTHREAD],[1],[Define if you have POSIX threads libraries and header files.])],[$1]) + : +else + ax_pthread_ok=no + $2 +fi +AC_LANG_POP +])dnl AX_PTHREAD -- GitLab