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liblzma: Use __attribute__((__constructor__)) if available.
This uses it for CRC table initializations when using --disable-small. It avoids mythread_once() overhead. It also means that then --disable-small --disable-threads is thread-safe if this attribute is supported.
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6553f49b11
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6 changed files with 59 additions and 5 deletions
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@ -48,6 +48,7 @@
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cmake_minimum_required(VERSION 3.13...3.16 FATAL_ERROR)
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include(CMakePushCheckState)
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include(CheckSymbolExists)
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include(CheckStructHasMember)
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include(cmake/tuklib_integer.cmake)
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@ -387,6 +388,20 @@ if(NOT TUKLIB_CPUCORES_FOUND OR NOT TUKLIB_PHYSMEM_FOUND)
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"To build anyway, edit this CMakeLists.txt to ignore this error.")
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endif()
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# Check for __attribute__((__constructor__)) support.
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# This needs -Werror because some compilers just warn
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# about this being unsupported.
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cmake_push_check_state()
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set(CMAKE_REQUIRED_FLAGS "-Werror")
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check_c_source_compiles("
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__attribute__((__constructor__))
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static void my_constructor_func(void) { return; }
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int main(void) { return 0; }
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"
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HAVE_FUNC_ATTRIBUTE_CONSTRUCTOR)
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cmake_pop_check_state()
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tuklib_add_definition_if(liblzma HAVE_FUNC_ATTRIBUTE_CONSTRUCTOR)
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# immintrin.h:
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include(CheckIncludeFile)
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check_include_file(immintrin.h HAVE_IMMINTRIN_H)
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4
INSTALL
4
INSTALL
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@ -456,7 +456,9 @@ XZ Utils Installation
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no Disable threading support. This is the
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same as using --disable-threads.
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NOTE: If combined with --enable-small, the
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NOTE: If combined with --enable-small
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and the compiler doesn't support
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__attribute__((__constructor__)), the
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resulting liblzma won't be thread safe,
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that is, if a multi-threaded application
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calls any liblzma functions from more than
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31
configure.ac
31
configure.ac
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@ -768,6 +768,29 @@ AC_CHECK_MEMBERS([
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AC_SYS_LARGEFILE
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AC_C_BIGENDIAN
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# __attribute__((__constructor__)) can be used for one-time initializations.
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# Use -Werror because some compilers accept unknown attributes and just
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# give a warning. If it works this should give no warnings, even
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# clang -Weverything should be fine.
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# dnl This doesn't need AC_LANG_SOURCE, minimal code is enough.
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AC_MSG_CHECKING([if __attribute__((__constructor__)) can be used])
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have_func_attribute_constructor=no
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OLD_CFLAGS="$CFLAGS"
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CFLAGS="$CFLAGS -Werror"
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AC_COMPILE_IFELSE([
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__attribute__((__constructor__))
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static void my_constructor_func(void) { return; }
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], [
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AC_DEFINE([HAVE_FUNC_ATTRIBUTE_CONSTRUCTOR], [1],
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[Define to 1 if __attribute__((__constructor__))
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is supported for functions.])
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have_func_attribute_constructor=yes
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AC_MSG_RESULT([yes])
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], [
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AC_MSG_RESULT([no])
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])
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CFLAGS="$OLD_CFLAGS"
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###############################################################################
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# Checks for library functions.
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@ -1005,9 +1028,11 @@ if test x$tuklib_cv_cpucores_method = xunknown; then
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echo "No supported method to detect the number of CPU cores."
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fi
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if test "x$enable_threads$enable_small" = xnoyes; then
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if test "x$enable_threads$enable_small$have_func_attribute_constructor" \
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= xnoyesno; then
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echo
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echo "NOTE:"
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echo "liblzma will be thread unsafe due the combination"
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echo "of --disable-threads --enable-small."
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echo "liblzma will be thread-unsafe due to the combination"
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echo "of --disable-threads --enable-small when using a compiler"
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echo "that doesn't support __attribute__((__constructor__))."
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fi
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@ -16,6 +16,9 @@
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uint32_t lzma_crc32_table[1][256];
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#ifdef HAVE_FUNC_ATTRIBUTE_CONSTRUCTOR
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__attribute__((__constructor__))
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#endif
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static void
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crc32_init(void)
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{
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@ -37,18 +40,22 @@ crc32_init(void)
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}
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#ifndef HAVE_FUNC_ATTRIBUTE_CONSTRUCTOR
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extern void
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lzma_crc32_init(void)
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{
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mythread_once(crc32_init);
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return;
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}
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#endif
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extern LZMA_API(uint32_t)
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lzma_crc32(const uint8_t *buf, size_t size, uint32_t crc)
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{
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#ifndef HAVE_FUNC_ATTRIBUTE_CONSTRUCTOR
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lzma_crc32_init();
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#endif
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crc = ~crc;
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@ -16,6 +16,9 @@
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static uint64_t crc64_table[256];
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#ifdef HAVE_FUNC_ATTRIBUTE_CONSTRUCTOR
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__attribute__((__constructor__))
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#endif
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static void
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crc64_init(void)
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{
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@ -40,7 +43,9 @@ crc64_init(void)
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extern LZMA_API(uint64_t)
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lzma_crc64(const uint8_t *buf, size_t size, uint64_t crc)
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{
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#ifndef HAVE_FUNC_ATTRIBUTE_CONSTRUCTOR
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mythread_once(crc64_init);
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#endif
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crc = ~crc;
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@ -543,7 +543,7 @@ lzma_lz_encoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
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const lzma_allocator *allocator, const void *options,
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lzma_lz_options *lz_options))
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{
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#ifdef HAVE_SMALL
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#if defined(HAVE_SMALL) && !defined(HAVE_FUNC_ATTRIBUTE_CONSTRUCTOR)
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// We need that the CRC32 table has been initialized.
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lzma_crc32_init();
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#endif
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