[FFmpeg-devel] [PATCH] configure: link to libatomic when it's present

[FFmpeg-devel] [PATCH] configure: link to libatomic when it's present

[Anton Khirnov]

C11 atomics in some configurations (e.g. 64bit operations on ppc64 with
GCC) require linking to libatomic.
---
Testing welcome, especially in configurations where
* libatomic is not present
* libatomic is actually needed
---
 configure | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/configure b/configure
index 1413122d87..1ff5dbee5b 100755
--- a/configure
+++ b/configure
@@ -6324,7 +6324,14 @@ check_headers asm/types.h
 # it seems there are versions of clang in some distros that try to use the
 # gcc headers, which explodes for stdatomic
 # so we also check that atomics actually work here
-check_builtin stdatomic stdatomic.h "atomic_int foo, bar = ATOMIC_VAR_INIT(-1); atomic_store(&foo, 0); foo += bar"
+#
+# some configurations also require linking to libatomic, so try
+# both with -latomic and without
+for LATOMIC in "-latomic" ""; do
+    check_builtin stdatomic stdatomic.h                                                 \
+        "atomic_int foo, bar = ATOMIC_VAR_INIT(-1); atomic_store(&foo, 0); foo += bar"  \
+        $LATOMIC && add_extralibs $LATOMIC && break
+done
 
 check_lib advapi32 "windows.h"            RegCloseKey          -ladvapi32
 check_lib bcrypt   "windows.h bcrypt.h"   BCryptGenRandom      -lbcrypt &&
-- 
2.33.0

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Re: [FFmpeg-devel] [PATCH] configure: link to libatomic when it's present

[James Almer]

On 1/19/2022 8:54 AM, Anton Khirnov wrote:
> C11 atomics in some configurations (e.g. 64bit operations on ppc64 with
> GCC) require linking to libatomic.
> ---
> Testing welcome, especially in configurations where
> * libatomic is not present
> * libatomic is actually needed
> ---
>   configure | 9 ++++++++-
>   1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/configure b/configure
> index 1413122d87..1ff5dbee5b 100755
> --- a/configure
> +++ b/configure
> @@ -6324,7 +6324,14 @@ check_headers asm/types.h
>   # it seems there are versions of clang in some distros that try to use the
>   # gcc headers, which explodes for stdatomic
>   # so we also check that atomics actually work here
> -check_builtin stdatomic stdatomic.h "atomic_int foo, bar = ATOMIC_VAR_INIT(-1); atomic_store(&foo, 0); foo += bar"
> +#
> +# some configurations also require linking to libatomic, so try
> +# both with -latomic and without
> +for LATOMIC in "-latomic" ""; do

Shouldn't you try without it first? On my toolchain libatomic is 
present, but libraries compile without linking to it just fine. That 
changes after this patch, where it starts linking to it explicitly.

> +    check_builtin stdatomic stdatomic.h                                                 \
> +        "atomic_int foo, bar = ATOMIC_VAR_INIT(-1); atomic_store(&foo, 0); foo += bar"  \
> +        $LATOMIC && add_extralibs $LATOMIC && break

You should probably add it to the required libraries' extralibs only.
Just replace the add_extralibs part with setting stdatomic_extralibs to 
$LATOMIC, and then add stdatomic to all the libraries' _suggest lists, 
same as we do for libm.

> +done
>   
>   check_lib advapi32 "windows.h"            RegCloseKey          -ladvapi32
>   check_lib bcrypt   "windows.h bcrypt.h"   BCryptGenRandom      -lbcrypt &&
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Re: [FFmpeg-devel] [PATCH] configure: link to libatomic when it's present

[Andreas Rheinhardt]

James Almer:
> 
> 
> On 1/19/2022 8:54 AM, Anton Khirnov wrote:
>> C11 atomics in some configurations (e.g. 64bit operations on ppc64 with
>> GCC) require linking to libatomic.
>> ---
>> Testing welcome, especially in configurations where
>> * libatomic is not present
>> * libatomic is actually needed
>> ---
>>   configure | 9 ++++++++-
>>   1 file changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/configure b/configure
>> index 1413122d87..1ff5dbee5b 100755
>> --- a/configure
>> +++ b/configure
>> @@ -6324,7 +6324,14 @@ check_headers asm/types.h
>>   # it seems there are versions of clang in some distros that try to
>> use the
>>   # gcc headers, which explodes for stdatomic
>>   # so we also check that atomics actually work here
>> -check_builtin stdatomic stdatomic.h "atomic_int foo, bar =
>> ATOMIC_VAR_INIT(-1); atomic_store(&foo, 0); foo += bar"
>> +#
>> +# some configurations also require linking to libatomic, so try
>> +# both with -latomic and without
>> +for LATOMIC in "-latomic" ""; do
> 
> Shouldn't you try without it first? On my toolchain libatomic is
> present, but libraries compile without linking to it just fine. That
> changes after this patch, where it starts linking to it explicitly.
> 

This would work if this test checked for all the atomic operations that
might be needed; but it doesn't: It checks just for atomic increment and
only for atomic_int. What is if atomic_increment can be done without
recourse to libatomic because of hardware support whereas another atomic
operation needs libatomic?

>> +    check_builtin stdatomic
>> stdatomic.h                                                 \
>> +        "atomic_int foo, bar = ATOMIC_VAR_INIT(-1);
>> atomic_store(&foo, 0); foo += bar"  \
>> +        $LATOMIC && add_extralibs $LATOMIC && break
> 
> You should probably add it to the required libraries' extralibs only.
> Just replace the add_extralibs part with setting stdatomic_extralibs to
> $LATOMIC, and then add stdatomic to all the libraries' _suggest lists,
> same as we do for libm.
> 
>> +done
>>     check_lib advapi32 "windows.h"            RegCloseKey         
>> -ladvapi32
>>   check_lib bcrypt   "windows.h bcrypt.h"   BCryptGenRandom     
>> -lbcrypt &&
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Re: [FFmpeg-devel] [PATCH] configure: link to libatomic when it's present

[Anton Khirnov]

Quoting James Almer (2022-01-19 13:34:20)
> 
> 
> On 1/19/2022 8:54 AM, Anton Khirnov wrote:
> > C11 atomics in some configurations (e.g. 64bit operations on ppc64 with
> > GCC) require linking to libatomic.
> > ---
> > Testing welcome, especially in configurations where
> > * libatomic is not present
> > * libatomic is actually needed
> > ---
> >   configure | 9 ++++++++-
> >   1 file changed, 8 insertions(+), 1 deletion(-)
> > 
> > diff --git a/configure b/configure
> > index 1413122d87..1ff5dbee5b 100755
> > --- a/configure
> > +++ b/configure
> > @@ -6324,7 +6324,14 @@ check_headers asm/types.h
> >   # it seems there are versions of clang in some distros that try to use the
> >   # gcc headers, which explodes for stdatomic
> >   # so we also check that atomics actually work here
> > -check_builtin stdatomic stdatomic.h "atomic_int foo, bar = ATOMIC_VAR_INIT(-1); atomic_store(&foo, 0); foo += bar"
> > +#
> > +# some configurations also require linking to libatomic, so try
> > +# both with -latomic and without
> > +for LATOMIC in "-latomic" ""; do
> 
> Shouldn't you try without it first? On my toolchain libatomic is 
> present, but libraries compile without linking to it just fine. That 
> changes after this patch, where it starts linking to it explicitly.

No, because it may only be needed for some atomic sizes and operations,
which the test in configure doesn't necessarily catch.
And because we pass as-needed to the linker, the built libraries
shouldn't actually require libatomic unless it's really needed.

> 
> > +    check_builtin stdatomic stdatomic.h                                                 \
> > +        "atomic_int foo, bar = ATOMIC_VAR_INIT(-1); atomic_store(&foo, 0); foo += bar"  \
> > +        $LATOMIC && add_extralibs $LATOMIC && break
> 
> You should probably add it to the required libraries' extralibs only.
> Just replace the add_extralibs part with setting stdatomic_extralibs to 
> $LATOMIC, and then add stdatomic to all the libraries' _suggest lists, 
> same as we do for libm.

Then we need to actively track which libraries actually use atomics,
which also depends on which features are enabled. Given that this only
fails on less-common arches, this sounds like a recipe for obscure build
failures. Given that it's only really linked when needed, it seems
better to just add it unconditionally.

-- 
Anton Khirnov
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Re: [FFmpeg-devel] [PATCH] configure: link to libatomic when it's present

[James Almer]

On 1/19/2022 9:40 AM, Anton Khirnov wrote:
> Quoting James Almer (2022-01-19 13:34:20)
>>
>>
>> On 1/19/2022 8:54 AM, Anton Khirnov wrote:
>>> C11 atomics in some configurations (e.g. 64bit operations on ppc64 with
>>> GCC) require linking to libatomic.
>>> ---
>>> Testing welcome, especially in configurations where
>>> * libatomic is not present
>>> * libatomic is actually needed
>>> ---
>>>    configure | 9 ++++++++-
>>>    1 file changed, 8 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/configure b/configure
>>> index 1413122d87..1ff5dbee5b 100755
>>> --- a/configure
>>> +++ b/configure
>>> @@ -6324,7 +6324,14 @@ check_headers asm/types.h
>>>    # it seems there are versions of clang in some distros that try to use the
>>>    # gcc headers, which explodes for stdatomic
>>>    # so we also check that atomics actually work here
>>> -check_builtin stdatomic stdatomic.h "atomic_int foo, bar = ATOMIC_VAR_INIT(-1); atomic_store(&foo, 0); foo += bar"
>>> +#
>>> +# some configurations also require linking to libatomic, so try
>>> +# both with -latomic and without
>>> +for LATOMIC in "-latomic" ""; do
>>
>> Shouldn't you try without it first? On my toolchain libatomic is
>> present, but libraries compile without linking to it just fine. That
>> changes after this patch, where it starts linking to it explicitly.
> 
> No, because it may only be needed for some atomic sizes and operations,
> which the test in configure doesn't necessarily catch.
> And because we pass as-needed to the linker, the built libraries
> shouldn't actually require libatomic unless it's really needed.

Ah, didn't consider --as-needed.

> 
>>
>>> +    check_builtin stdatomic stdatomic.h                                                 \
>>> +        "atomic_int foo, bar = ATOMIC_VAR_INIT(-1); atomic_store(&foo, 0); foo += bar"  \
>>> +        $LATOMIC && add_extralibs $LATOMIC && break
>>
>> You should probably add it to the required libraries' extralibs only.
>> Just replace the add_extralibs part with setting stdatomic_extralibs to
>> $LATOMIC, and then add stdatomic to all the libraries' _suggest lists,
>> same as we do for libm.
> 
> Then we need to actively track which libraries actually use atomics,
> which also depends on which features are enabled. Given that this only
> fails on less-common arches, this sounds like a recipe for obscure build
> failures. Given that it's only really linked when needed, it seems
> better to just add it unconditionally.

Then just add it to all of them, like we do for libm.

What i want to avoid is having it in EXTRALIBS. There was a huge 
configure rework long ago that removed everything from that variable 
(leaving it as the place where user defined --extra-libs arguments are 
dumped), and fine tuned ld arguments in a per library/module basis. I'd 
like to not go back to start dumping everything in EXTRALIBS.

Like this, on top of this patch:

> diff --git a/configure b/configure
> index 1ff5dbee5b..43713a7679 100755
> --- a/configure
> +++ b/configure
> @@ -3794,20 +3794,20 @@ cws2fws_extralibs="zlib_extralibs"
> 
>  # libraries, in any order
>  avcodec_deps="avutil"
> -avcodec_suggest="libm"
> +avcodec_suggest="libm stdatomic"
>  avdevice_deps="avformat avcodec avutil"
> -avdevice_suggest="libm"
> +avdevice_suggest="libm stdatomic"
>  avfilter_deps="avutil"
> -avfilter_suggest="libm"
> +avfilter_suggest="libm stdatomic"
>  avformat_deps="avcodec avutil"
> -avformat_suggest="libm network zlib"
> -avutil_suggest="clock_gettime ffnvcodec libm libdrm libmfx opencl user32 vaapi vulkan videotoolbox corefoundation corevideo coremedia bcrypt"
> +avformat_suggest="libm network stdatomic zlib"
> +avutil_suggest="clock_gettime ffnvcodec libm libdrm libmfx opencl stdatomic user32 vaapi vulkan videotoolbox corefoundation corevideo coremedia bcrypt"
>  postproc_deps="avutil gpl"
> -postproc_suggest="libm"
> +postproc_suggest="libm stdatomic"
>  swresample_deps="avutil"
> -swresample_suggest="libm libsoxr"
> +swresample_suggest="libm libsoxr stdatomic"
>  swscale_deps="avutil"
> -swscale_suggest="libm"
> +swscale_suggest="libm stdatomic"
> 
>  avcodec_extralibs="pthreads_extralibs iconv_extralibs dxva2_extralibs"
>  avfilter_extralibs="pthreads_extralibs"
> @@ -6330,7 +6330,7 @@ check_headers asm/types.h
>  for LATOMIC in "-latomic" ""; do
>      check_builtin stdatomic stdatomic.h                                                 \
>          "atomic_int foo, bar = ATOMIC_VAR_INIT(-1); atomic_store(&foo, 0); foo += bar"  \
> -        $LATOMIC && add_extralibs $LATOMIC && break
> +        $LATOMIC && eval stdatomic_extralibs="\$LATOMIC" && break
>  done
> 
>  check_lib advapi32 "windows.h"            RegCloseKey          -ladvapi32
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[FFmpeg-devel] [PATCH] configure: link to libatomic when it's present

[Anton Khirnov]

C11 atomics in some configurations (e.g. 64bit operations on ppc64 with
GCC) require linking to libatomic.

Fixes #9275
---
 configure | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/configure b/configure
index 1413122d87..3059c154df 100755
--- a/configure
+++ b/configure
@@ -3794,20 +3794,20 @@ cws2fws_extralibs="zlib_extralibs"
 
 # libraries, in any order
 avcodec_deps="avutil"
-avcodec_suggest="libm"
+avcodec_suggest="libm stdatomic"
 avdevice_deps="avformat avcodec avutil"
-avdevice_suggest="libm"
+avdevice_suggest="libm stdatomic"
 avfilter_deps="avutil"
-avfilter_suggest="libm"
+avfilter_suggest="libm stdatomic"
 avformat_deps="avcodec avutil"
-avformat_suggest="libm network zlib"
-avutil_suggest="clock_gettime ffnvcodec libm libdrm libmfx opencl user32 vaapi vulkan videotoolbox corefoundation corevideo coremedia bcrypt"
+avformat_suggest="libm network zlib stdatomic"
+avutil_suggest="clock_gettime ffnvcodec libm libdrm libmfx opencl user32 vaapi vulkan videotoolbox corefoundation corevideo coremedia bcrypt stdatomic"
 postproc_deps="avutil gpl"
-postproc_suggest="libm"
+postproc_suggest="libm stdatomic"
 swresample_deps="avutil"
-swresample_suggest="libm libsoxr"
+swresample_suggest="libm libsoxr stdatomic"
 swscale_deps="avutil"
-swscale_suggest="libm"
+swscale_suggest="libm stdatomic"
 
 avcodec_extralibs="pthreads_extralibs iconv_extralibs dxva2_extralibs"
 avfilter_extralibs="pthreads_extralibs"
@@ -6324,7 +6324,14 @@ check_headers asm/types.h
 # it seems there are versions of clang in some distros that try to use the
 # gcc headers, which explodes for stdatomic
 # so we also check that atomics actually work here
-check_builtin stdatomic stdatomic.h "atomic_int foo, bar = ATOMIC_VAR_INIT(-1); atomic_store(&foo, 0); foo += bar"
+#
+# some configurations also require linking to libatomic, so try
+# both with -latomic and without
+for LATOMIC in "-latomic" ""; do
+    check_builtin stdatomic stdatomic.h                                                 \
+        "atomic_int foo, bar = ATOMIC_VAR_INIT(-1); atomic_store(&foo, 0); foo += bar"  \
+        $LATOMIC && eval stdatomic_extralibs="\$LATOMIC" && break
+done
 
 check_lib advapi32 "windows.h"            RegCloseKey          -ladvapi32
 check_lib bcrypt   "windows.h bcrypt.h"   BCryptGenRandom      -lbcrypt &&
-- 
2.33.0

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Re: [FFmpeg-devel] [PATCH] configure: link to libatomic when it's present

[James Almer]

On 1/19/2022 10:48 AM, Anton Khirnov wrote:
> C11 atomics in some configurations (e.g. 64bit operations on ppc64 with
> GCC) require linking to libatomic.
> 
> Fixes #9275
> ---
>   configure | 25 ++++++++++++++++---------
>   1 file changed, 16 insertions(+), 9 deletions(-)
> 
> diff --git a/configure b/configure
> index 1413122d87..3059c154df 100755
> --- a/configure
> +++ b/configure
> @@ -3794,20 +3794,20 @@ cws2fws_extralibs="zlib_extralibs"
>   
>   # libraries, in any order
>   avcodec_deps="avutil"
> -avcodec_suggest="libm"
> +avcodec_suggest="libm stdatomic"
>   avdevice_deps="avformat avcodec avutil"
> -avdevice_suggest="libm"
> +avdevice_suggest="libm stdatomic"
>   avfilter_deps="avutil"
> -avfilter_suggest="libm"
> +avfilter_suggest="libm stdatomic"
>   avformat_deps="avcodec avutil"
> -avformat_suggest="libm network zlib"
> -avutil_suggest="clock_gettime ffnvcodec libm libdrm libmfx opencl user32 vaapi vulkan videotoolbox corefoundation corevideo coremedia bcrypt"
> +avformat_suggest="libm network zlib stdatomic"
> +avutil_suggest="clock_gettime ffnvcodec libm libdrm libmfx opencl user32 vaapi vulkan videotoolbox corefoundation corevideo coremedia bcrypt stdatomic"
>   postproc_deps="avutil gpl"
> -postproc_suggest="libm"
> +postproc_suggest="libm stdatomic"
>   swresample_deps="avutil"
> -swresample_suggest="libm libsoxr"
> +swresample_suggest="libm libsoxr stdatomic"
>   swscale_deps="avutil"
> -swscale_suggest="libm"
> +swscale_suggest="libm stdatomic"
>   
>   avcodec_extralibs="pthreads_extralibs iconv_extralibs dxva2_extralibs"
>   avfilter_extralibs="pthreads_extralibs"
> @@ -6324,7 +6324,14 @@ check_headers asm/types.h
>   # it seems there are versions of clang in some distros that try to use the
>   # gcc headers, which explodes for stdatomic
>   # so we also check that atomics actually work here
> -check_builtin stdatomic stdatomic.h "atomic_int foo, bar = ATOMIC_VAR_INIT(-1); atomic_store(&foo, 0); foo += bar"
> +#
> +# some configurations also require linking to libatomic, so try
> +# both with -latomic and without
> +for LATOMIC in "-latomic" ""; do
> +    check_builtin stdatomic stdatomic.h                                                 \
> +        "atomic_int foo, bar = ATOMIC_VAR_INIT(-1); atomic_store(&foo, 0); foo += bar"  \
> +        $LATOMIC && eval stdatomic_extralibs="\$LATOMIC" && break
> +done

LGTM now, thanks.

>   
>   check_lib advapi32 "windows.h"            RegCloseKey          -ladvapi32
>   check_lib bcrypt   "windows.h bcrypt.h"   BCryptGenRandom      -lbcrypt &&
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Re: [FFmpeg-devel] [PATCH] configure: link to libatomic when it's present

[Brad Smith]

On 1/19/2022 10:23 AM, James Almer wrote:

> On 1/19/2022 10:48 AM, Anton Khirnov wrote:
>> C11 atomics in some configurations (e.g. 64bit operations on ppc64 with
>> GCC) require linking to libatomic.
>>
>> Fixes #9275
>> ---
>>   configure | 25 ++++++++++++++++---------
>>   1 file changed, 16 insertions(+), 9 deletions(-)
>>
>> diff --git a/configure b/configure
>> index 1413122d87..3059c154df 100755
>> --- a/configure
>> +++ b/configure
>> @@ -3794,20 +3794,20 @@ cws2fws_extralibs="zlib_extralibs"
>>     # libraries, in any order
>>   avcodec_deps="avutil"
>> -avcodec_suggest="libm"
>> +avcodec_suggest="libm stdatomic"
>>   avdevice_deps="avformat avcodec avutil"
>> -avdevice_suggest="libm"
>> +avdevice_suggest="libm stdatomic"
>>   avfilter_deps="avutil"
>> -avfilter_suggest="libm"
>> +avfilter_suggest="libm stdatomic"
>>   avformat_deps="avcodec avutil"
>> -avformat_suggest="libm network zlib"
>> -avutil_suggest="clock_gettime ffnvcodec libm libdrm libmfx opencl 
>> user32 vaapi vulkan videotoolbox corefoundation corevideo coremedia 
>> bcrypt"
>> +avformat_suggest="libm network zlib stdatomic"
>> +avutil_suggest="clock_gettime ffnvcodec libm libdrm libmfx opencl 
>> user32 vaapi vulkan videotoolbox corefoundation corevideo coremedia 
>> bcrypt stdatomic"
>>   postproc_deps="avutil gpl"
>> -postproc_suggest="libm"
>> +postproc_suggest="libm stdatomic"
>>   swresample_deps="avutil"
>> -swresample_suggest="libm libsoxr"
>> +swresample_suggest="libm libsoxr stdatomic"
>>   swscale_deps="avutil"
>> -swscale_suggest="libm"
>> +swscale_suggest="libm stdatomic"
>>     avcodec_extralibs="pthreads_extralibs iconv_extralibs 
>> dxva2_extralibs"
>>   avfilter_extralibs="pthreads_extralibs"
>> @@ -6324,7 +6324,14 @@ check_headers asm/types.h
>>   # it seems there are versions of clang in some distros that try to 
>> use the
>>   # gcc headers, which explodes for stdatomic
>>   # so we also check that atomics actually work here
>> -check_builtin stdatomic stdatomic.h "atomic_int foo, bar = 
>> ATOMIC_VAR_INIT(-1); atomic_store(&foo, 0); foo += bar"
>> +#
>> +# some configurations also require linking to libatomic, so try
>> +# both with -latomic and without
>> +for LATOMIC in "-latomic" ""; do
>> +    check_builtin stdatomic 
>> stdatomic.h                                                 \
>> +        "atomic_int foo, bar = ATOMIC_VAR_INIT(-1); 
>> atomic_store(&foo, 0); foo += bar"  \
>> +        $LATOMIC && eval stdatomic_extralibs="\$LATOMIC" && break
>> +done
>
> LGTM now, thanks.
>
>>     check_lib advapi32 "windows.h"            RegCloseKey          
>> -ladvapi32
>>   check_lib bcrypt   "windows.h bcrypt.h"   BCryptGenRandom -lbcrypt &&

Wait, this should be checking without first then with, if the first test 
without fails.

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Re: [FFmpeg-devel] [PATCH] configure: link to libatomic when it's present

[Hendrik Leppkes]

On Sat, Jan 22, 2022 at 7:43 AM Brad Smith
<brad-at-comstyle.com@ffmpeg.org> wrote:
>
> On 1/19/2022 10:23 AM, James Almer wrote:
>
> > On 1/19/2022 10:48 AM, Anton Khirnov wrote:
> >> C11 atomics in some configurations (e.g. 64bit operations on ppc64 with
> >> GCC) require linking to libatomic.
> >>
> >> Fixes #9275
> >> ---
> >>   configure | 25 ++++++++++++++++---------
> >>   1 file changed, 16 insertions(+), 9 deletions(-)
> >>
> >> diff --git a/configure b/configure
> >> index 1413122d87..3059c154df 100755
> >> --- a/configure
> >> +++ b/configure
> >> @@ -3794,20 +3794,20 @@ cws2fws_extralibs="zlib_extralibs"
> >>     # libraries, in any order
> >>   avcodec_deps="avutil"
> >> -avcodec_suggest="libm"
> >> +avcodec_suggest="libm stdatomic"
> >>   avdevice_deps="avformat avcodec avutil"
> >> -avdevice_suggest="libm"
> >> +avdevice_suggest="libm stdatomic"
> >>   avfilter_deps="avutil"
> >> -avfilter_suggest="libm"
> >> +avfilter_suggest="libm stdatomic"
> >>   avformat_deps="avcodec avutil"
> >> -avformat_suggest="libm network zlib"
> >> -avutil_suggest="clock_gettime ffnvcodec libm libdrm libmfx opencl
> >> user32 vaapi vulkan videotoolbox corefoundation corevideo coremedia
> >> bcrypt"
> >> +avformat_suggest="libm network zlib stdatomic"
> >> +avutil_suggest="clock_gettime ffnvcodec libm libdrm libmfx opencl
> >> user32 vaapi vulkan videotoolbox corefoundation corevideo coremedia
> >> bcrypt stdatomic"
> >>   postproc_deps="avutil gpl"
> >> -postproc_suggest="libm"
> >> +postproc_suggest="libm stdatomic"
> >>   swresample_deps="avutil"
> >> -swresample_suggest="libm libsoxr"
> >> +swresample_suggest="libm libsoxr stdatomic"
> >>   swscale_deps="avutil"
> >> -swscale_suggest="libm"
> >> +swscale_suggest="libm stdatomic"
> >>     avcodec_extralibs="pthreads_extralibs iconv_extralibs
> >> dxva2_extralibs"
> >>   avfilter_extralibs="pthreads_extralibs"
> >> @@ -6324,7 +6324,14 @@ check_headers asm/types.h
> >>   # it seems there are versions of clang in some distros that try to
> >> use the
> >>   # gcc headers, which explodes for stdatomic
> >>   # so we also check that atomics actually work here
> >> -check_builtin stdatomic stdatomic.h "atomic_int foo, bar =
> >> ATOMIC_VAR_INIT(-1); atomic_store(&foo, 0); foo += bar"
> >> +#
> >> +# some configurations also require linking to libatomic, so try
> >> +# both with -latomic and without
> >> +for LATOMIC in "-latomic" ""; do
> >> +    check_builtin stdatomic
> >> stdatomic.h                                                 \
> >> +        "atomic_int foo, bar = ATOMIC_VAR_INIT(-1);
> >> atomic_store(&foo, 0); foo += bar"  \
> >> +        $LATOMIC && eval stdatomic_extralibs="\$LATOMIC" && break
> >> +done
> >
> > LGTM now, thanks.
> >
> >>     check_lib advapi32 "windows.h"            RegCloseKey
> >> -ladvapi32
> >>   check_lib bcrypt   "windows.h bcrypt.h"   BCryptGenRandom -lbcrypt &&
>
> Wait, this should be checking without first then with, if the first test
> without fails.
>

This was covered earlier in the thread for the reason it is not - its
deliberate, because exhaustive functionality checks would be very
complicated.

- Hendrik
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Re: [FFmpeg-devel] [PATCH] configure: link to libatomic when it's present

[Brad Smith]

On 1/22/2022 4:00 AM, Hendrik Leppkes wrote:

> On Sat, Jan 22, 2022 at 7:43 AM Brad Smith
> <brad-at-comstyle.com@ffmpeg.org>  wrote:
>> On 1/19/2022 10:23 AM, James Almer wrote:
>>
>>> On 1/19/2022 10:48 AM, Anton Khirnov wrote:
>>>> C11 atomics in some configurations (e.g. 64bit operations on ppc64 with
>>>> GCC) require linking to libatomic.
>>>>
>>>> Fixes #9275
>>>> ---
>>>>    configure | 25 ++++++++++++++++---------
>>>>    1 file changed, 16 insertions(+), 9 deletions(-)
>>>>
>>>> diff --git a/configure b/configure
>>>> index 1413122d87..3059c154df 100755
>>>> --- a/configure
>>>> +++ b/configure
>>>> @@ -3794,20 +3794,20 @@ cws2fws_extralibs="zlib_extralibs"
>>>>      # libraries, in any order
>>>>    avcodec_deps="avutil"
>>>> -avcodec_suggest="libm"
>>>> +avcodec_suggest="libm stdatomic"
>>>>    avdevice_deps="avformat avcodec avutil"
>>>> -avdevice_suggest="libm"
>>>> +avdevice_suggest="libm stdatomic"
>>>>    avfilter_deps="avutil"
>>>> -avfilter_suggest="libm"
>>>> +avfilter_suggest="libm stdatomic"
>>>>    avformat_deps="avcodec avutil"
>>>> -avformat_suggest="libm network zlib"
>>>> -avutil_suggest="clock_gettime ffnvcodec libm libdrm libmfx opencl
>>>> user32 vaapi vulkan videotoolbox corefoundation corevideo coremedia
>>>> bcrypt"
>>>> +avformat_suggest="libm network zlib stdatomic"
>>>> +avutil_suggest="clock_gettime ffnvcodec libm libdrm libmfx opencl
>>>> user32 vaapi vulkan videotoolbox corefoundation corevideo coremedia
>>>> bcrypt stdatomic"
>>>>    postproc_deps="avutil gpl"
>>>> -postproc_suggest="libm"
>>>> +postproc_suggest="libm stdatomic"
>>>>    swresample_deps="avutil"
>>>> -swresample_suggest="libm libsoxr"
>>>> +swresample_suggest="libm libsoxr stdatomic"
>>>>    swscale_deps="avutil"
>>>> -swscale_suggest="libm"
>>>> +swscale_suggest="libm stdatomic"
>>>>      avcodec_extralibs="pthreads_extralibs iconv_extralibs
>>>> dxva2_extralibs"
>>>>    avfilter_extralibs="pthreads_extralibs"
>>>> @@ -6324,7 +6324,14 @@ check_headers asm/types.h
>>>>    # it seems there are versions of clang in some distros that try to
>>>> use the
>>>>    # gcc headers, which explodes for stdatomic
>>>>    # so we also check that atomics actually work here
>>>> -check_builtin stdatomic stdatomic.h "atomic_int foo, bar =
>>>> ATOMIC_VAR_INIT(-1); atomic_store(&foo, 0); foo += bar"
>>>> +#
>>>> +# some configurations also require linking to libatomic, so try
>>>> +# both with -latomic and without
>>>> +for LATOMIC in "-latomic" ""; do
>>>> +    check_builtin stdatomic
>>>> stdatomic.h                                                 \
>>>> +        "atomic_int foo, bar = ATOMIC_VAR_INIT(-1);
>>>> atomic_store(&foo, 0); foo += bar"  \
>>>> +        $LATOMIC && eval stdatomic_extralibs="\$LATOMIC" && break
>>>> +done
>>> LGTM now, thanks.
>>>
>>>>      check_lib advapi32 "windows.h"            RegCloseKey
>>>> -ladvapi32
>>>>    check_lib bcrypt   "windows.h bcrypt.h"   BCryptGenRandom -lbcrypt &&
>> Wait, this should be checking without first then with, if the first test
>> without fails.
>>
> This was covered earlier in the thread for the reason it is not - its
> deliberate, because exhaustive functionality checks would be very
> complicated.

Testing this commit out it does as I had suspected and even with --as-needed
causes a false positive on OpenBSD / FreeBSD.  Now erroneously tries to link
against libatomic and unlike the other project (haproxy) I ran across an 
overly
simplistic test (doesn't even involve linking, just checking compiler 
predefined
macros) I don't see any options to disable the broken test either.
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Re: [FFmpeg-devel] [PATCH] configure: link to libatomic when it's present

[Anton Khirnov]

Quoting Brad Smith (2022-01-23 20:40:30)
> 
> Testing this commit out it does as I had suspected and even with --as-needed
> causes a false positive on OpenBSD / FreeBSD.

Why?

-- 
Anton Khirnov
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Re: [FFmpeg-devel] [PATCH] configure: link to libatomic when it's present

[Brad Smith]

On 1/26/2022 6:49 AM, Anton Khirnov wrote:

> Quoting Brad Smith (2022-01-23 20:40:30)
>> Testing this commit out it does as I had suspected and even with --as-needed
>> causes a false positive on OpenBSD / FreeBSD.
> Why?

Looking at this again and thinking about what it does, the test as is is 
flawed.
With the order being used it doesn't check to see if  the linked binary even
is linked against libatomic. Using --as-needed it drops the libatomic 
dependency
but since the link succeeds then the code as it is and based on the 
ordering, as
I commented about, says go ahead and link in libatomic. Changing the order
so it is "" "-latomic" instead of "-latomic" "" does the right thing.

humpty$ cc -D_ISOC99_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE 
-DPIC -O2 -pipe -I/usr/local/include -I/usr/X11R6/include -std=c11 -fPIC 
-c -o test.o test.c
humpty$ cc -Wl,--as-needed -Wl,-z,noexecstack -o test test.o -latomic 
-L/usr/local/lib -L/usr/X11R6/lib
humpty$ objdump -p test

test:     file format elf64-x86-64

Program Header:
     PHDR off    0x0000000000000040 vaddr 0x0000000000000040 paddr 
0x0000000000000040 align 2**3
          filesz 0x00000000000002a0 memsz 0x00000000000002a0 flags r--
   INTERP off    0x00000000000002e0 vaddr 0x00000000000002e0 paddr 
0x00000000000002e0 align 2**0
          filesz 0x0000000000000013 memsz 0x0000000000000013 flags r--
     LOAD off    0x0000000000000000 vaddr 0x0000000000000000 paddr 
0x0000000000000000 align 2**12
          filesz 0x00000000000005dc memsz 0x00000000000005dc flags r--
     LOAD off    0x00000000000005e0 vaddr 0x00000000000015e0 paddr 
0x00000000000015e0 align 2**12
          filesz 0x0000000000000450 memsz 0x0000000000000450 flags r-x
     LOAD off    0x0000000000000a30 vaddr 0x0000000000002a30 paddr 
0x0000000000002a30 align 2**12
          filesz 0x00000000000001c0 memsz 0x00000000000001c0 flags rw-
     LOAD off    0x0000000000000bf0 vaddr 0x0000000000003bf0 paddr 
0x0000000000003bf0 align 2**12
          filesz 0x0000000000000000 memsz 0x0000000000000055 flags rw-
  DYNAMIC off    0x0000000000000a88 vaddr 0x0000000000002a88 paddr 
0x0000000000002a88 align 2**3
          filesz 0x0000000000000120 memsz 0x0000000000000120 flags rw-
    RELRO off    0x0000000000000a30 vaddr 0x0000000000002a30 paddr 
0x0000000000002a30 align 2**0
          filesz 0x00000000000001c0 memsz 0x00000000000005d0 flags r--
EH_FRAME off    0x00000000000004c8 vaddr 0x00000000000004c8 paddr 
0x00000000000004c8 align 2**2
          filesz 0x0000000000000034 memsz 0x0000000000000034 flags r--
OPENBSD_RANDOMIZE off    0x0000000000000a30 vaddr 0x0000000000002a30 
paddr 0x0000000000002a30 align 2**3
          filesz 0x0000000000000030 memsz 0x0000000000000030 flags rw-
    STACK off    0x0000000000000000 vaddr 0x0000000000000000 paddr 
0x0000000000000000 align 2**0
          filesz 0x0000000000000000 memsz 0x0000000000000000 flags rw-
     NOTE off    0x00000000000002f4 vaddr 0x00000000000002f4 paddr 
0x00000000000002f4 align 2**2
          filesz 0x0000000000000018 memsz 0x0000000000000018 flags r--

Dynamic Section:
   NEEDED      libc.so.96.1
   FLAGS_1     0x8000000
   DEBUG       0x0
   RELA        0x438
   RELASZ      0x30
   RELAENT     0x18
   RELACOUNT   0x1
   JMPREL      0x468
   PLTRELSZ    0x60
   PLTGOT      0x2bb8
   PLTREL      0x7
   SYMTAB      0x310
   SYMENT      0x18
   STRTAB      0x3f8
   STRSZ       0x3f
   GNU_HASH    0x3a0
   HASH        0x3c0

libatomic is dropped by --as-needed since it is not necessary.

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Re: [FFmpeg-devel] [PATCH] configure: link to libatomic when it's present

[Hendrik Leppkes]

On Sat, Jan 29, 2022 at 5:45 AM Brad Smith
<brad-at-comstyle.com@ffmpeg.org> wrote:
>
> libatomic is dropped by --as-needed since it is not necessary.
>

Thats what this solution relies on, and thus there is no harm in adding it.

- Hendrik
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Re: [FFmpeg-devel] [PATCH] configure: link to libatomic when it's present

[Brad Smith]

On 1/29/2022 4:54 AM, Hendrik Leppkes wrote:

> On Sat, Jan 29, 2022 at 5:45 AM Brad Smith
> <brad-at-comstyle.com@ffmpeg.org> wrote:
>> libatomic is dropped by --as-needed since it is not necessary.
>>
> Thats what this solution relies on, and thus there is no harm in adding it.

But it doesn't work, and the generated pkg-config files are contaminated 
too. I'll just
have to patch out this broken crap locally.
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Re: [FFmpeg-devel] [PATCH] configure: link to libatomic when it's present

[Anton Khirnov]

Quoting Brad Smith (2022-01-29 19:15:46)
> On 1/29/2022 4:54 AM, Hendrik Leppkes wrote:
> 
> > On Sat, Jan 29, 2022 at 5:45 AM Brad Smith
> > <brad-at-comstyle.com@ffmpeg.org> wrote:
> >> libatomic is dropped by --as-needed since it is not necessary.
> >>
> > Thats what this solution relies on, and thus there is no harm in adding it.
> 
> But it doesn't work, and the generated pkg-config files are contaminated 
> too. I'll just
> have to patch out this broken crap locally.

You have now twice disregarded someone explaining why the test first
check with -latomic and then without, then you call this code "broken
crap" without properly explaining what breaks and why.

Consider communicating better if you want people here to take you
seriously.

-- 
Anton Khirnov
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