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build: Check for std::atomic::exchange rather than std::atomic_exchange

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Our usage of std::atomic is with it's own exchange function, not
std::atomic_exchange. So we should be looking specifically for that
function.

Additionally, -pthread and -lpthread have an effect on whether -latomic
will be needed, so the atomics check needs to use these flags as well.
This will make the flags in use better match what is actually used when
linking.

This removes the need for -latomic for riscv builds, which resolves a
guix cross architecture reproducibility issue.
This commit is contained in:
Andrew Chow 2022-07-11 20:26:25 -04:00
parent c92eb6cda0
commit 4de4221ab4
2 changed files with 7 additions and 4 deletions
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5
build-aux/m4/l_atomic.m4
View file

@ -18,7 +18,7 @@ m4_define([_CHECK_ATOMIC_testbody], [[
int main() {
std::atomic<bool> lock{true};
std::atomic_exchange(&lock, false);
lock.exchange(false);
std::atomic<std::chrono::seconds> t{0s};
t.store(2s);
@ -34,6 +34,8 @@ m4_define([_CHECK_ATOMIC_testbody], [[
AC_DEFUN([CHECK_ATOMIC], [
AC_LANG_PUSH(C++)
TEMP_CXXFLAGS="$CXXFLAGS"
CXXFLAGS="$CXXFLAGS $PTHREAD_CFLAGS"
AC_MSG_CHECKING([whether std::atomic can be used without link library])
@ -51,5 +53,6 @@ AC_DEFUN([CHECK_ATOMIC], [
])
])
CXXFLAGS="$TEMP_CXXFLAGS"
AC_LANG_POP
])

6
configure.ac
View file

@ -87,9 +87,6 @@ else
AX_CXX_COMPILE_STDCXX([20], [noext], [mandatory])
fi
dnl Check if -latomic is required for <std::atomic>
CHECK_ATOMIC
dnl check if additional link flags are required for std::filesystem
CHECK_FILESYSTEM
@ -887,6 +884,9 @@ AC_C_BIGENDIAN
dnl Check for pthread compile/link requirements
AX_PTHREAD
dnl Check if -latomic is required for <std::atomic>
CHECK_ATOMIC
dnl The following macro will add the necessary defines to bitcoin-config.h, but
dnl they also need to be passed down to any subprojects. Pull the results out of
dnl the cache and add them to CPPFLAGS.