And now I left the CHROMIUM tag, sorry ,-(
On Thu, Mar 29, 2018 at 4:31 PM, Nicolas Boichat <drink...@chromium.org> wrote:
> From: Nicolas Boichat <drink...@chromium.org>
>
> When compiling with LLVM 6.0, the test fails to detect that
> -latomic is actually required, as the atomic call is inlined.
>
> In the code itself (src/util/disk_cache.c), we see this pattern:
> p_atomic_add(cache->size, - (uint64_t)size);
> where cache->size is an uint64_t *, and results in the following
> link time error without -latomic:
> src/util/disk_cache.c:628: error: undefined reference to
> '__atomic_fetch_add_8'
>
> Fix the configure/meson test to replicate this pattern, which then
> correctly realizes the need for -latomic.
>
> Signed-off-by: Nicolas Boichat <drink...@chromium.org>
> ---
>
> Changes since v1:
> - Updated meson.build as well (untested)
>
> configure.ac | 6 ++++--
> meson.build | 6 ++++--
> 2 files changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/configure.ac b/configure.ac
> index e874f8ebfb2..eff9a0ef88f 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -445,9 +445,11 @@ if test "x$GCC_ATOMIC_BUILTINS_SUPPORTED" = x1; then
> AC_MSG_CHECKING(whether -latomic is needed)
> AC_LINK_IFELSE([AC_LANG_SOURCE([[
> #include <stdint.h>
> - uint64_t v;
> + struct {
> + uint64_t* v;
> + } x;
> int main() {
> - return (int)__atomic_load_n(&v, __ATOMIC_ACQUIRE);
> + return (int)__atomic_load_n(x.v, __ATOMIC_ACQUIRE);
> }]])], GCC_ATOMIC_BUILTINS_NEED_LIBATOMIC=no,
> GCC_ATOMIC_BUILTINS_NEED_LIBATOMIC=yes)
> AC_MSG_RESULT($GCC_ATOMIC_BUILTINS_NEED_LIBATOMIC)
> if test "x$GCC_ATOMIC_BUILTINS_NEED_LIBATOMIC" = xyes; then
> diff --git a/meson.build b/meson.build
> index f210eeb2530..cd567dc000e 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -850,8 +850,10 @@ if cc.compiles('int main() { int n; return
> __atomic_load_n(&n, __ATOMIC_ACQUIRE)
> # as ARM.
> if not cc.links('''#include <stdint.h>
> int main() {
> - uint64_t n;
> - return (int)__atomic_load_n(&n, __ATOMIC_ACQUIRE);
> + struct {
> + uint64_t *v;
> + } x;
> + return (int)__atomic_load_n(x.v, __ATOMIC_ACQUIRE);
> }''',
> name : 'GCC atomic builtins required -latomic')
> dep_atomic = cc.find_library('atomic')
> --
> 2.17.0.rc1.321.gba9d0f2565-goog
>
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