[FFmpeg-devel] [PATCH] configure: add -fno-semantic-interposition to optflags

[FFmpeg-devel] [PATCH] configure: add -fno-semantic-interposition to optflags

[Anton Khirnov]

Gcc flag -fsemantic-interposition, which is on by default with current
gcc versions, makes the compiler assume exported symbols can be
interposed by the linker, which prevents various kinds of optimization.

Since we do not support such interposition and disable it with
-Bsymbolic, explicitly disable this assumption.
---
 configure | 1 +
 1 file changed, 1 insertion(+)

diff --git a/configure b/configure
index cb895cf9ac..6f702bfb64 100755
--- a/configure
+++ b/configure
@@ -7174,6 +7174,7 @@ check_optflags(){
 check_optflags $optflags
 check_optflags -fno-math-errno
 check_optflags -fno-signed-zeros
+check_optflags -fno-semantic-interposition
 
 if enabled lto; then
     test "$cc_type" != "$ld_type" && die "LTO requires same compiler and linker"
-- 
2.35.1

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Re: [FFmpeg-devel] [PATCH] configure: add -fno-semantic-interposition to optflags

[Andreas Rheinhardt]

Anton Khirnov:
> Gcc flag -fsemantic-interposition, which is on by default with current
> gcc versions, makes the compiler assume exported symbols can be
> interposed by the linker, which prevents various kinds of optimization.
> 
> Since we do not support such interposition and disable it with
> -Bsymbolic, explicitly disable this assumption.
> ---
>  configure | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/configure b/configure
> index cb895cf9ac..6f702bfb64 100755
> --- a/configure
> +++ b/configure
> @@ -7174,6 +7174,7 @@ check_optflags(){
>  check_optflags $optflags
>  check_optflags -fno-math-errno
>  check_optflags -fno-signed-zeros
> +check_optflags -fno-semantic-interposition
>  
>  if enabled lto; then
>      test "$cc_type" != "$ld_type" && die "LTO requires same compiler and linker"

This will add lots of dead HEVC functions in x86/hevcdsp_init.c; at
least it did this last time I checked: Several of these functions are
then inlined and because there are no callers outside of it, these
functions are dead code. Of course marking them as static would be
preferable, but that easier said than done with these macros.

- Andreas

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