[FFmpeg-devel] [PATCH] ffbuild: read library linker objects from a file

[FFmpeg-devel] [PATCH] ffbuild: read library linker objects from a file

[Gyan Doshi]

The linker command can exceed the maximum argument limit on MinGW,
especially for libavcodec.

The objects list is now stored in a file and passed to the linker.
---
 ffbuild/library.mak | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/ffbuild/library.mak b/ffbuild/library.mak
index 793e9d41fa..781b018e00 100644
--- a/ffbuild/library.mak
+++ b/ffbuild/library.mak
@@ -66,8 +66,10 @@ $(SUBDIR)$(SLIBNAME): $(SUBDIR)$(SLIBNAME_WITH_MAJOR)
 
 $(SUBDIR)$(SLIBNAME_WITH_MAJOR): $(OBJS) $(SHLIBOBJS) $(SLIBOBJS) $(SUBDIR)lib$(NAME).ver
 	$(SLIB_CREATE_DEF_CMD)
-	$$(LD) $(SHFLAGS) $(LDFLAGS) $(LDSOFLAGS) $$(LD_O) $$(filter %.o,$$^) $(FFEXTRALIBS)
+	$(Q)echo $$(filter %.o,$$^) > $$@.objs
+	$$(LD) $(SHFLAGS) $(LDFLAGS) $(LDSOFLAGS) $$(LD_O) @$$@.objs $(FFEXTRALIBS)
 	$(SLIB_EXTRA_CMD)
+	-$(RM) $$@.objs
 
 ifdef SUBDIR
 $(SUBDIR)$(SLIBNAME_WITH_MAJOR): $(DEP_LIBS)
-- 
2.46.1

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Re: [FFmpeg-devel] [PATCH] ffbuild: read library linker objects from a file

[Martin Storsjö]

On Wed, 12 Mar 2025, Gyan Doshi wrote:

> The linker command can exceed the maximum argument limit on MinGW,
> especially for libavcodec.
>
> The objects list is now stored in a file and passed to the linker.
> ---
> ffbuild/library.mak | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/ffbuild/library.mak b/ffbuild/library.mak
> index 793e9d41fa..781b018e00 100644
> --- a/ffbuild/library.mak
> +++ b/ffbuild/library.mak
> @@ -66,8 +66,10 @@ $(SUBDIR)$(SLIBNAME): $(SUBDIR)$(SLIBNAME_WITH_MAJOR)
>
> $(SUBDIR)$(SLIBNAME_WITH_MAJOR): $(OBJS) $(SHLIBOBJS) $(SLIBOBJS) $(SUBDIR)lib$(NAME).ver
> 	$(SLIB_CREATE_DEF_CMD)
> -	$$(LD) $(SHFLAGS) $(LDFLAGS) $(LDSOFLAGS) $$(LD_O) $$(filter %.o,$$^) $(FFEXTRALIBS)
> +	$(Q)echo $$(filter %.o,$$^) > $$@.objs
> +	$$(LD) $(SHFLAGS) $(LDFLAGS) $(LDSOFLAGS) $$(LD_O) @$$@.objs $(FFEXTRALIBS)
> 	$(SLIB_EXTRA_CMD)
> +	-$(RM) $$@.objs

Don't we need do the same for static libraries too?

On first glance, this looks quite reasonable... However, the limit that is 
an issue is the length of a command line. The .objs file is written with 
an "echo" command - doesn't that fundamentally also hit the same limit 
(just a little bit later, as there are fewer command line flags in this 
command)?

Or do we assume that make executes it with a shell, where the shell 
handles "echo" as a shell builtin so that it doesn't actually spawn a 
subprocess for this? Can you test it, if you could extend the list of 
object files to the point where the .objs file is clearly over 32 KB, and 
verify that it did include all the files you intended?

Secondly, less fundamental - even if we try to remove the .objs file here 
at the same time it's quite possible for it to be left behind (e.g. if the 
linking command fails) - so it would be good to make sure that it is 
removed on "make clean" too.

Plus we probably should include it in .gitignore, if someone does in-tree 
builds.

// Martin

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Re: [FFmpeg-devel] [PATCH] ffbuild: read library linker objects from a file

[Gyan Doshi]

On 2025-03-12 01:29 pm, Martin Storsjö wrote:
> On Wed, 12 Mar 2025, Gyan Doshi wrote:
>
>> The linker command can exceed the maximum argument limit on MinGW,
>> especially for libavcodec.
>>
>> The objects list is now stored in a file and passed to the linker.
>> ---
>> ffbuild/library.mak | 4 +++-
>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/ffbuild/library.mak b/ffbuild/library.mak
>> index 793e9d41fa..781b018e00 100644
>> --- a/ffbuild/library.mak
>> +++ b/ffbuild/library.mak
>> @@ -66,8 +66,10 @@ $(SUBDIR)$(SLIBNAME): $(SUBDIR)$(SLIBNAME_WITH_MAJOR)
>>
>> $(SUBDIR)$(SLIBNAME_WITH_MAJOR): $(OBJS) $(SHLIBOBJS) $(SLIBOBJS) 
>> $(SUBDIR)lib$(NAME).ver
>>     $(SLIB_CREATE_DEF_CMD)
>> -    $$(LD) $(SHFLAGS) $(LDFLAGS) $(LDSOFLAGS) $$(LD_O) $$(filter 
>> %.o,$$^) $(FFEXTRALIBS)
>> +    $(Q)echo $$(filter %.o,$$^) > $$@.objs
>> +    $$(LD) $(SHFLAGS) $(LDFLAGS) $(LDSOFLAGS) $$(LD_O) @$$@.objs 
>> $(FFEXTRALIBS)
>>     $(SLIB_EXTRA_CMD)
>> +    -$(RM) $$@.objs
>
> Don't we need do the same for static libraries too?
>
> On first glance, this looks quite reasonable... However, the limit 
> that is an issue is the length of a command line. The .objs file is 
> written with an "echo" command - doesn't that fundamentally also hit 
> the same limit (just a little bit later, as there are fewer command 
> line flags in this command)?
>
> Or do we assume that make executes it with a shell, where the shell 
> handles "echo" as a shell builtin so that it doesn't actually spawn a 
> subprocess for this? Can you test it, if you could extend the list of 
> object files to the point where the .objs file is clearly over 32 KB, 
> and verify that it did include all the files you intended?

The specific error I got when building a shared build of 7.1.1 (with ~90 
external libs) was

/bin/sh: line 1: /mingw64/bin/ccache: Argument list too long

Got same error without ccache.

The static build of the same config succeeded without any patching.
The .objs file generated for libavcodec shared build is 29KB.

How do I inflate the size to above 32K? I've enabled pretty much 
everything I can.


> Secondly, less fundamental - even if we try to remove the .objs file 
> here at the same time it's quite possible for it to be left behind 
> (e.g. if the linking command fails) - so it would be good to make sure 
> that it is removed on "make clean" too.
>
> Plus we probably should include it in .gitignore, if someone does 
> in-tree builds.

Will add both.

Regards,
Gyan

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Re: [FFmpeg-devel] [PATCH] ffbuild: read library linker objects from a file

[Martin Storsjö]

On Wed, 12 Mar 2025, Gyan Doshi wrote:

> On 2025-03-12 01:29 pm, Martin Storsjö wrote:
>> On Wed, 12 Mar 2025, Gyan Doshi wrote:
>>
>>> The linker command can exceed the maximum argument limit on MinGW,
>>> especially for libavcodec.
>>>
>>> The objects list is now stored in a file and passed to the linker.
>>> ---
>>> ffbuild/library.mak | 4 +++-
>>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/ffbuild/library.mak b/ffbuild/library.mak
>>> index 793e9d41fa..781b018e00 100644
>>> --- a/ffbuild/library.mak
>>> +++ b/ffbuild/library.mak
>>> @@ -66,8 +66,10 @@ $(SUBDIR)$(SLIBNAME): $(SUBDIR)$(SLIBNAME_WITH_MAJOR)
>>>
>>> $(SUBDIR)$(SLIBNAME_WITH_MAJOR): $(OBJS) $(SHLIBOBJS) $(SLIBOBJS) 
>>> $(SUBDIR)lib$(NAME).ver
>>>     $(SLIB_CREATE_DEF_CMD)
>>> -    $$(LD) $(SHFLAGS) $(LDFLAGS) $(LDSOFLAGS) $$(LD_O) $$(filter 
>>> %.o,$$^) $(FFEXTRALIBS)
>>> +    $(Q)echo $$(filter %.o,$$^) > $$@.objs
>>> +    $$(LD) $(SHFLAGS) $(LDFLAGS) $(LDSOFLAGS) $$(LD_O) @$$@.objs 
>>> $(FFEXTRALIBS)
>>>     $(SLIB_EXTRA_CMD)
>>> +    -$(RM) $$@.objs
>>
>> Don't we need do the same for static libraries too?
>>
>> On first glance, this looks quite reasonable... However, the limit 
>> that is an issue is the length of a command line. The .objs file is 
>> written with an "echo" command - doesn't that fundamentally also hit 
>> the same limit (just a little bit later, as there are fewer command 
>> line flags in this command)?
>>
>> Or do we assume that make executes it with a shell, where the shell 
>> handles "echo" as a shell builtin so that it doesn't actually spawn a 
>> subprocess for this? Can you test it, if you could extend the list of 
>> object files to the point where the .objs file is clearly over 32 KB, 
>> and verify that it did include all the files you intended?
>
> The specific error I got when building a shared build of 7.1.1 (with ~90 
> external libs) was
>
> /bin/sh: line 1: /mingw64/bin/ccache: Argument list too long
>
> Got same error without ccache.
>
> The static build of the same config succeeded without any patching.
> The .objs file generated for libavcodec shared build is 29KB.
>
> How do I inflate the size to above 32K? I've enabled pretty much 
> everything I can.

The simplest would probably be to add a bunch of empty .c files (with long 
file names) in libavcodec and hook them up in the makefile. We won't 
notice if they are missed when linking of course, but if we pass the 
command line length limit, we should still notice it in one way or 
another.

// Martin
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Re: [FFmpeg-devel] [PATCH] ffbuild: read library linker objects from a file

[Gyan Doshi]

On 2025-03-12 03:12 pm, Martin Storsjö wrote:
> On Wed, 12 Mar 2025, Gyan Doshi wrote:
>
>> On 2025-03-12 01:29 pm, Martin Storsjö wrote:
>>> On Wed, 12 Mar 2025, Gyan Doshi wrote:
>>>
>>>> The linker command can exceed the maximum argument limit on MinGW,
>>>> especially for libavcodec.
>>>>
>>>> The objects list is now stored in a file and passed to the linker.
>>>> ---
>>>> ffbuild/library.mak | 4 +++-
>>>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/ffbuild/library.mak b/ffbuild/library.mak
>>>> index 793e9d41fa..781b018e00 100644
>>>> --- a/ffbuild/library.mak
>>>> +++ b/ffbuild/library.mak
>>>> @@ -66,8 +66,10 @@ $(SUBDIR)$(SLIBNAME): 
>>>> $(SUBDIR)$(SLIBNAME_WITH_MAJOR)
>>>>
>>>> $(SUBDIR)$(SLIBNAME_WITH_MAJOR): $(OBJS) $(SHLIBOBJS) $(SLIBOBJS) 
>>>> $(SUBDIR)lib$(NAME).ver
>>>>     $(SLIB_CREATE_DEF_CMD)
>>>> -    $$(LD) $(SHFLAGS) $(LDFLAGS) $(LDSOFLAGS) $$(LD_O) $$(filter 
>>>> %.o,$$^) $(FFEXTRALIBS)
>>>> +    $(Q)echo $$(filter %.o,$$^) > $$@.objs
>>>> +    $$(LD) $(SHFLAGS) $(LDFLAGS) $(LDSOFLAGS) $$(LD_O) @$$@.objs 
>>>> $(FFEXTRALIBS)
>>>>     $(SLIB_EXTRA_CMD)
>>>> +    -$(RM) $$@.objs
>>>
>>> Don't we need do the same for static libraries too?
>>>
>>> On first glance, this looks quite reasonable... However, the limit 
>>> that is an issue is the length of a command line. The .objs file is 
>>> written with an "echo" command - doesn't that fundamentally also hit 
>>> the same limit (just a little bit later, as there are fewer command 
>>> line flags in this command)?
>>>
>>> Or do we assume that make executes it with a shell, where the shell 
>>> handles "echo" as a shell builtin so that it doesn't actually spawn 
>>> a subprocess for this? Can you test it, if you could extend the list 
>>> of object files to the point where the .objs file is clearly over 32 
>>> KB, and verify that it did include all the files you intended?
>>
>> The specific error I got when building a shared build of 7.1.1 (with 
>> ~90 external libs) was
>>
>> /bin/sh: line 1: /mingw64/bin/ccache: Argument list too long
>>
>> Got same error without ccache.
>>
>> The static build of the same config succeeded without any patching.
>> The .objs file generated for libavcodec shared build is 29KB.
>>
>> How do I inflate the size to above 32K? I've enabled pretty much 
>> everything I can.
>
> The simplest would probably be to add a bunch of empty .c files (with 
> long file names) in libavcodec and hook them up in the makefile. We 
> won't notice if they are missed when linking of course, but if we pass 
> the command line length limit, we should still notice it in one way or 
> another.

I did something simpler. I just duplicated the arg on the echo line. The 
build was successful. Each objs file was twice as big, same for the 
generated DLL.
Does that answer your queries?

Regards,
Gyan

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Re: [FFmpeg-devel] [PATCH] ffbuild: read library linker objects from a file

[Zhao Zhili]

> On Mar 12, 2025, at 16:34, Gyan Doshi <ffmpeg@gyani.pro> wrote:
> 
> 
> 
> On 2025-03-12 01:29 pm, Martin Storsjö wrote:
>> On Wed, 12 Mar 2025, Gyan Doshi wrote:
>> 
>>> The linker command can exceed the maximum argument limit on MinGW,
>>> especially for libavcodec.
>>> 
>>> The objects list is now stored in a file and passed to the linker.
>>> ---
>>> ffbuild/library.mak | 4 +++-
>>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>> 
>>> diff --git a/ffbuild/library.mak b/ffbuild/library.mak
>>> index 793e9d41fa..781b018e00 100644
>>> --- a/ffbuild/library.mak
>>> +++ b/ffbuild/library.mak
>>> @@ -66,8 +66,10 @@ $(SUBDIR)$(SLIBNAME): $(SUBDIR)$(SLIBNAME_WITH_MAJOR)
>>> 
>>> $(SUBDIR)$(SLIBNAME_WITH_MAJOR): $(OBJS) $(SHLIBOBJS) $(SLIBOBJS) $(SUBDIR)lib$(NAME).ver
>>>     $(SLIB_CREATE_DEF_CMD)
>>> -    $$(LD) $(SHFLAGS) $(LDFLAGS) $(LDSOFLAGS) $$(LD_O) $$(filter %.o,$$^) $(FFEXTRALIBS)
>>> +    $(Q)echo $$(filter %.o,$$^) > $$@.objs
>>> +    $$(LD) $(SHFLAGS) $(LDFLAGS) $(LDSOFLAGS) $$(LD_O) @$$@.objs $(FFEXTRALIBS)
>>>     $(SLIB_EXTRA_CMD)
>>> +    -$(RM) $$@.objs
>> 
>> Don't we need do the same for static libraries too?
>> 
>> On first glance, this looks quite reasonable... However, the limit that is an issue is the length of a command line. The .objs file is written with an "echo" command - doesn't that fundamentally also hit the same limit (just a little bit later, as there are fewer command line flags in this command)?
>> 
>> Or do we assume that make executes it with a shell, where the shell handles "echo" as a shell builtin so that it doesn't actually spawn a subprocess for this? Can you test it, if you could extend the list of object files to the point where the .objs file is clearly over 32 KB, and verify that it did include all the files you intended?
> 
> The specific error I got when building a shared build of 7.1.1 (with ~90 external libs) was
> 
> /bin/sh: line 1: /mingw64/bin/ccache: Argument list too long

I have got the same error from user’s report, but I cannot reproduce the error by myself.

FYI, there is a meson port of ffmpeg in gstreamer. It’s about five times faster than configure+make on Windows. Maybe not a ready for build and release binary, but can save a lot of time when developing and test.

https://gitlab.freedesktop.org/gstreamer/meson-ports/ffmpeg

> 
> Got same error without ccache.
> 
> The static build of the same config succeeded without any patching.
> The .objs file generated for libavcodec shared build is 29KB.
> 
> How do I inflate the size to above 32K? I've enabled pretty much everything I can.
> 
> 
>> Secondly, less fundamental - even if we try to remove the .objs file here at the same time it's quite possible for it to be left behind (e.g. if the linking command fails) - so it would be good to make sure that it is removed on "make clean" too.
>> 
>> Plus we probably should include it in .gitignore, if someone does in-tree builds.
> 
> Will add both.
> 
> Regards,
> Gyan
> 
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel@ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> 
> To unsubscribe, visit link above, or email
> ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".

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Re: [FFmpeg-devel] [PATCH] ffbuild: read library linker objects from a file

[Martin Storsjö]

On Wed, 12 Mar 2025, Gyan Doshi wrote:

> On 2025-03-12 03:12 pm, Martin Storsjö wrote:
>> On Wed, 12 Mar 2025, Gyan Doshi wrote:
>>
>>> On 2025-03-12 01:29 pm, Martin Storsjö wrote:
>>>> On Wed, 12 Mar 2025, Gyan Doshi wrote:
>>>>
>>>>> The linker command can exceed the maximum argument limit on MinGW,
>>>>> especially for libavcodec.
>>>>>
>>>>> The objects list is now stored in a file and passed to the linker.
>>>>> ---
>>>>> ffbuild/library.mak | 4 +++-
>>>>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/ffbuild/library.mak b/ffbuild/library.mak
>>>>> index 793e9d41fa..781b018e00 100644
>>>>> --- a/ffbuild/library.mak
>>>>> +++ b/ffbuild/library.mak
>>>>> @@ -66,8 +66,10 @@ $(SUBDIR)$(SLIBNAME): 
>>>>> $(SUBDIR)$(SLIBNAME_WITH_MAJOR)
>>>>>
>>>>> $(SUBDIR)$(SLIBNAME_WITH_MAJOR): $(OBJS) $(SHLIBOBJS) $(SLIBOBJS) 
>>>>> $(SUBDIR)lib$(NAME).ver
>>>>>     $(SLIB_CREATE_DEF_CMD)
>>>>> -    $$(LD) $(SHFLAGS) $(LDFLAGS) $(LDSOFLAGS) $$(LD_O) $$(filter 
>>>>> %.o,$$^) $(FFEXTRALIBS)
>>>>> +    $(Q)echo $$(filter %.o,$$^) > $$@.objs
>>>>> +    $$(LD) $(SHFLAGS) $(LDFLAGS) $(LDSOFLAGS) $$(LD_O) @$$@.objs 
>>>>> $(FFEXTRALIBS)
>>>>>     $(SLIB_EXTRA_CMD)
>>>>> +    -$(RM) $$@.objs
>>>>
>>>> Don't we need do the same for static libraries too?
>>>>
>>>> On first glance, this looks quite reasonable... However, the limit 
>>>> that is an issue is the length of a command line. The .objs file is 
>>>> written with an "echo" command - doesn't that fundamentally also hit 
>>>> the same limit (just a little bit later, as there are fewer command 
>>>> line flags in this command)?
>>>>
>>>> Or do we assume that make executes it with a shell, where the shell 
>>>> handles "echo" as a shell builtin so that it doesn't actually spawn 
>>>> a subprocess for this? Can you test it, if you could extend the list 
>>>> of object files to the point where the .objs file is clearly over 32 
>>>> KB, and verify that it did include all the files you intended?
>>>
>>> The specific error I got when building a shared build of 7.1.1 (with 
>>> ~90 external libs) was
>>>
>>> /bin/sh: line 1: /mingw64/bin/ccache: Argument list too long
>>>
>>> Got same error without ccache.
>>>
>>> The static build of the same config succeeded without any patching.
>>> The .objs file generated for libavcodec shared build is 29KB.
>>>
>>> How do I inflate the size to above 32K? I've enabled pretty much 
>>> everything I can.
>>
>> The simplest would probably be to add a bunch of empty .c files (with 
>> long file names) in libavcodec and hook them up in the makefile. We 
>> won't notice if they are missed when linking of course, but if we pass 
>> the command line length limit, we should still notice it in one way or 
>> another.
>
> I did something simpler. I just duplicated the arg on the echo line. The 
> build was successful. Each objs file was twice as big, same for the 
> generated DLL.
> Does that answer your queries?

Yes, thanks.

Btw, just to be clear - are you running this in msys2? If you're running 
mingw build tools via WSL, there wouldn't be any issue when running the 
shell commands on the linux side, but it's specifically with the msys2 
make where it's interesting to know which limitations make and the shell 
runs into or avoids.

// Martin
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Re: [FFmpeg-devel] [PATCH] ffbuild: read library linker objects from a file

[Gyan Doshi]

On 2025-03-12 05:52 pm, Martin Storsjö wrote:
> On Wed, 12 Mar 2025, Gyan Doshi wrote:
>
>> On 2025-03-12 03:12 pm, Martin Storsjö wrote:
>>> On Wed, 12 Mar 2025, Gyan Doshi wrote:
>>>
>>>> On 2025-03-12 01:29 pm, Martin Storsjö wrote:
>>>>> On Wed, 12 Mar 2025, Gyan Doshi wrote:
>>>>>
>>>>>> The linker command can exceed the maximum argument limit on MinGW,
>>>>>> especially for libavcodec.
>>>>>>
>>>>>> The objects list is now stored in a file and passed to the linker.
>>>>>> ---
>>>>>> ffbuild/library.mak | 4 +++-
>>>>>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>>>>>
>>>>>> diff --git a/ffbuild/library.mak b/ffbuild/library.mak
>>>>>> index 793e9d41fa..781b018e00 100644
>>>>>> --- a/ffbuild/library.mak
>>>>>> +++ b/ffbuild/library.mak
>>>>>> @@ -66,8 +66,10 @@ $(SUBDIR)$(SLIBNAME): 
>>>>>> $(SUBDIR)$(SLIBNAME_WITH_MAJOR)
>>>>>>
>>>>>> $(SUBDIR)$(SLIBNAME_WITH_MAJOR): $(OBJS) $(SHLIBOBJS) $(SLIBOBJS) 
>>>>>> $(SUBDIR)lib$(NAME).ver
>>>>>>     $(SLIB_CREATE_DEF_CMD)
>>>>>> -    $$(LD) $(SHFLAGS) $(LDFLAGS) $(LDSOFLAGS) $$(LD_O) $$(filter 
>>>>>> %.o,$$^) $(FFEXTRALIBS)
>>>>>> +    $(Q)echo $$(filter %.o,$$^) > $$@.objs
>>>>>> +    $$(LD) $(SHFLAGS) $(LDFLAGS) $(LDSOFLAGS) $$(LD_O) @$$@.objs 
>>>>>> $(FFEXTRALIBS)
>>>>>>     $(SLIB_EXTRA_CMD)
>>>>>> +    -$(RM) $$@.objs
>>>>>
>>>>> Don't we need do the same for static libraries too?
>>>>>
>>>>> On first glance, this looks quite reasonable... However, the limit 
>>>>> that is an issue is the length of a command line. The .objs file 
>>>>> is written with an "echo" command - doesn't that fundamentally 
>>>>> also hit the same limit (just a little bit later, as there are 
>>>>> fewer command line flags in this command)?
>>>>>
>>>>> Or do we assume that make executes it with a shell, where the 
>>>>> shell handles "echo" as a shell builtin so that it doesn't 
>>>>> actually spawn a subprocess for this? Can you test it, if you 
>>>>> could extend the list of object files to the point where the .objs 
>>>>> file is clearly over 32 KB, and verify that it did include all the 
>>>>> files you intended?
>>>>
>>>> The specific error I got when building a shared build of 7.1.1 
>>>> (with ~90 external libs) was
>>>>
>>>> /bin/sh: line 1: /mingw64/bin/ccache: Argument list too long
>>>>
>>>> Got same error without ccache.
>>>>
>>>> The static build of the same config succeeded without any patching.
>>>> The .objs file generated for libavcodec shared build is 29KB.
>>>>
>>>> How do I inflate the size to above 32K? I've enabled pretty much 
>>>> everything I can.
>>>
>>> The simplest would probably be to add a bunch of empty .c files 
>>> (with long file names) in libavcodec and hook them up in the 
>>> makefile. We won't notice if they are missed when linking of course, 
>>> but if we pass the command line length limit, we should still notice 
>>> it in one way or another.
>>
>> I did something simpler. I just duplicated the arg on the echo line. 
>> The build was successful. Each objs file was twice as big, same for 
>> the generated DLL.
>> Does that answer your queries?
>
> Yes, thanks.
>
> Btw, just to be clear - are you running this in msys2? If you're 
> running mingw build tools via WSL, there wouldn't be any issue when 
> running the shell commands on the linux side, but it's specifically 
> with the msys2 make where it's interesting to know which limitations 
> make and the shell runs into or avoids.

Yes, via msys2.

This is what `xargs --show-limits` prints in the same shell,

POSIX upper limit on argument length (this system): 25382
POSIX smallest allowable upper limit on argument length (all systems): 4096
Maximum length of command we could actually use: 20812
Size of command buffer we are actually using: 25382

Regards,
Gyan

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