Author: saugustine Date: Mon May 13 11:45:03 2019 New Revision: 360610 URL: http://llvm.org/viewvc/llvm-project?rev=360610&view=rev Log: Add a new LIBUNWIND_WEAK_PTHREAD Cmake option to force calls into the pthread library use weak symbols.
This option allows libpthread to be a weak dependency rather than a hard one. Differential Revision: https://reviews.llvm.org/D60285 Modified: libunwind/trunk/CMakeLists.txt libunwind/trunk/src/CMakeLists.txt libunwind/trunk/src/RWMutex.hpp Modified: libunwind/trunk/CMakeLists.txt URL: http://llvm.org/viewvc/llvm-project/libunwind/trunk/CMakeLists.txt?rev=360610&r1=360609&r2=360610&view=diff ============================================================================== --- libunwind/trunk/CMakeLists.txt (original) +++ libunwind/trunk/CMakeLists.txt Mon May 13 11:45:03 2019 @@ -134,6 +134,7 @@ option(LIBUNWIND_ENABLE_STATIC "Build li option(LIBUNWIND_ENABLE_CROSS_UNWINDING "Enable cross-platform unwinding support." OFF) option(LIBUNWIND_ENABLE_ARM_WMMX "Enable unwinding support for ARM WMMX registers." OFF) option(LIBUNWIND_ENABLE_THREADS "Build libunwind with threading support." ON) +option(LIBUNWIND_WEAK_PTHREAD_LIB "Use weak references to refer to pthread functions." OFF) option(LIBUNWIND_USE_COMPILER_RT "Use compiler-rt instead of libgcc" OFF) option(LIBUNWIND_INCLUDE_DOCS "Build the libunwind documentation." ${LLVM_INCLUDE_DOCS}) Modified: libunwind/trunk/src/CMakeLists.txt URL: http://llvm.org/viewvc/llvm-project/libunwind/trunk/src/CMakeLists.txt?rev=360610&r1=360609&r2=360610&view=diff ============================================================================== --- libunwind/trunk/src/CMakeLists.txt (original) +++ libunwind/trunk/src/CMakeLists.txt Mon May 13 11:45:03 2019 @@ -67,6 +67,7 @@ endif() unwind_append_if(libraries LIBUNWIND_HAS_DL_LIB dl) if (LIBUNWIND_ENABLE_THREADS) unwind_append_if(libraries LIBUNWIND_HAS_PTHREAD_LIB pthread) + unwind_append_if(LIBUNWIND_COMPILE_FLAGS LIBUNWIND_WEAK_PTHREAD_LIB -DLIBUNWIND_USE_WEAK_PTHREAD=1) endif() # Setup flags. Modified: libunwind/trunk/src/RWMutex.hpp URL: http://llvm.org/viewvc/llvm-project/libunwind/trunk/src/RWMutex.hpp?rev=360610&r1=360609&r2=360610&view=diff ============================================================================== --- libunwind/trunk/src/RWMutex.hpp (original) +++ libunwind/trunk/src/RWMutex.hpp Mon May 13 11:45:03 2019 @@ -56,17 +56,52 @@ private: SRWLOCK _lock = SRWLOCK_INIT; }; -#else +#elif !defined(LIBUNWIND_USE_WEAK_PTHREAD) class _LIBUNWIND_HIDDEN RWMutex { public: - bool lock_shared() { return pthread_rwlock_rdlock(&_lock) == 0; } + bool lock_shared() { return pthread_rwlock_rdlock(&_lock) == 0; } bool unlock_shared() { return pthread_rwlock_unlock(&_lock) == 0; } bool lock() { return pthread_rwlock_wrlock(&_lock) == 0; } bool unlock() { return pthread_rwlock_unlock(&_lock) == 0; } private: pthread_rwlock_t _lock = PTHREAD_RWLOCK_INITIALIZER; +}; + +#else + +extern "C" int __attribute__((weak)) +pthread_create(pthread_t *thread, const pthread_attr_t *attr, + void *(*start_routine)(void *), void *arg); +extern "C" int __attribute__((weak)) +pthread_rwlock_rdlock(pthread_rwlock_t *lock); +extern "C" int __attribute__((weak)) +pthread_rwlock_wrlock(pthread_rwlock_t *lock); +extern "C" int __attribute__((weak)) +pthread_rwlock_unlock(pthread_rwlock_t *lock); + +// Calls to the locking functions are gated on pthread_create, and not the +// functions themselves, because the data structure should only be locked if +// another thread has been created. This is what similar libraries do. + +class _LIBUNWIND_HIDDEN RWMutex { +public: + bool lock_shared() { + return !pthread_create || (pthread_rwlock_rdlock(&_lock) == 0); + } + bool unlock_shared() { + return !pthread_create || (pthread_rwlock_unlock(&_lock) == 0); + } + bool lock() { + return !pthread_create || (pthread_rwlock_wrlock(&_lock) == 0); + } + bool unlock() { + return !pthread_create || (pthread_rwlock_unlock(&_lock) == 0); + } + +private: + pthread_rwlock_t _lock = PTHREAD_RWLOCK_INITIALIZER; }; #endif _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
