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| author | Jia Tan <jiat0218@gmail.com> | 2023-08-09 20:35:16 +0800 |
|---|---|---|
| committer | Jia Tan <jiat0218@gmail.com> | 2023-08-09 20:35:16 +0800 |
| commit | de574404c4c2f87aca049f232c38526e3ce092aa (patch) | |
| tree | 0d00acb0e9a0627a3741c2d2b1382c19f5880710 | |
| parent | mythread.h: Fix typo error in Vista threads mythread_once(). (diff) | |
| download | xz-de574404c4c2f87aca049f232c38526e3ce092aa.tar.xz | |
Build: Conditionally allow win95 threads and --enable-small.
When the compiler supports __attribute__((__constructor__))
mythread_once() is never used, even with --enable-small. A configuration
with win95 threads and --enable-small will compile and be thread safe so
it can be allowed.
This isn't a very common configuration since MSVC does not support
__attribute__((__constructor__)), but MINGW32 and CLANG32 environments
for MSYS2 can use win95 threads and have
__attribute__((__constructor__)) support.
| -rw-r--r-- | configure.ac | 21 |
1 files changed, 13 insertions, 8 deletions
diff --git a/configure.ac b/configure.ac index 8470e3e8..905d717f 100644 --- a/configure.ac +++ b/configure.ac @@ -437,14 +437,6 @@ case $enable_threads in ;; esac -# The Win95 threading lacks thread-safe one-time initialization function. -# It's better to disallow it instead of allowing threaded but thread-unsafe -# build. -if test "x$enable_small$enable_threads" = xyeswin95; then - AC_MSG_ERROR([--enable-threads=win95 and --enable-small cannot be - used at the same time]) -fi - # We use the actual result a little later. @@ -861,6 +853,19 @@ AC_COMPILE_IFELSE([ ]) CFLAGS="$OLD_CFLAGS" +# The Win95 threading lacks a thread-safe one-time initialization function. +# The one-time initialization is needed for crc32_small.c and crc64_small.c +# create the CRC tables. So if small mode is enabled, the threading mode is +# win95, and the compiler does not support attribute constructor, then we +# would end up with a multithreaded build that is thread-unsafe. As a +# result this configuration is not allowed. +if test "x$enable_small$enable_threads$have_func_attribute_constructor"\ + = xyeswin95no; then + AC_MSG_ERROR([--enable-threads=win95 and --enable-small cannot be + used at the same time with a compiler that doesn't support + __attribute__((__constructor__))]) +fi + # __attribute__((__ifunc__())) can be used to choose between different # implementations of the same function at runtime. This is slightly more # efficient than using __attribute__((__constructor__)) and setting |