bug#57420: 29.0.50; Failure configuring Emacs with animated WebP support

bug#57420: 29.0.50; Failure configuring Emacs with animated WebP support

[Daniel Martín via Bug reports for GNU Emacs, the Swiss army knife of text editors]

I have a computer that cannot build Emacs since the animated WebP
support was added.

Details of the system:

aarch64-apple-darwin21.1.0, NS appkit-2113.00 Version 12.0.1 (Build
21A559)
Windowing system distributor 'Apple', version 10.3.2113
System Description:  macOS 12.4

Library WebP is installed via the Homebrew package manager.

$ pkg-config --libs libwebp

-L/opt/homebrew/Cellar/webp/1.2.2/lib -lwebp

Steps to reproduce the problem:

make -j

[...]

checking for libwebp >= 0.6.0... yes

[...]

ld: library not found for -lwebp
clang: error: linker command failed with exit code 1 (use -v to see invocation)

One workaround I've been using to build Emacs is to configure it
--with-webp=no

I think this is a bug that was introduced when animated WebP support was
added.  From commit d82e1a873df381b2c35bc9036da5665468bdfd31:

diff --git a/configure.ac b/configure.ac
index 6b834a2f65..185e4d0862 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2695,6 +2695,9 @@ AC_DEFUN
       WEBP_MODULE="libwebp >= $WEBP_REQUIRED"
 
       EMACS_CHECK_MODULES([WEBP], [$WEBP_MODULE])
+      if test "$HAVE_WEBP" = "yes"; then
+        WEBP_LIBS="-lwebp -lwebpdemux"
+      fi
       AC_SUBST(WEBP_CFLAGS)
       AC_SUBST(WEBP_LIBS)
    fi

The problem I see with this part of the patch is that, after you call
EMACS_CHECK_MODULES, the variable WEBP_LIBS is correctly set to
"-L/opt/homebrew/Cellar/webp/1.2.2/lib -lwebp" via pkg-config.  However,
it is overriden to contain "-lwebp -lwebpdemux", so the library path got
removed.

If WebP animated support requires -lwebpdemux, I think we could require
the libwebpdemux module instead (part of the libwebp package), whose
linker flags include "-lwebp -lwebpdemux".  The following patch fixes
the compilation for me:

diff --git a/configure.ac b/configure.ac
index 6ca3052ea3..4590ed3506 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2773,12 +2773,9 @@ AC_DEFUN
    || test "${HAVE_W32}" = "yes" || test "${HAVE_NS}" = "yes" \
    || test "${HAVE_BE_APP}" = "yes" || test "${HAVE_PGTK}" = "yes"; then
       WEBP_REQUIRED=0.6.0
-      WEBP_MODULE="libwebp >= $WEBP_REQUIRED"
+      WEBP_MODULE="libwebpdemux >= $WEBP_REQUIRED"
 
       EMACS_CHECK_MODULES([WEBP], [$WEBP_MODULE])
-      if test "$HAVE_WEBP" = "yes"; then
-        WEBP_LIBS="-lwebp -lwebpdemux"
-      fi
       AC_SUBST([WEBP_CFLAGS])
       AC_SUBST([WEBP_LIBS])
    fi

I checked that the built Emacs has WebP support.

What do you think? I'd need an build system expert to verify that this
is TRT in GNU/Linux, Windows, or when pkg-config is not available.

bug#57420: 29.0.50; Failure configuring Emacs with animated WebP support

[Stefan Kangas]

Daniel Martín via "Bug reports for GNU Emacs, the Swiss army knife of
text editors" <bug-gnu-emacs@gnu.org> writes:

> I checked that the built Emacs has WebP support.
>
> What do you think? I'd need an build system expert to verify that this
> is TRT in GNU/Linux, Windows, or when pkg-config is not available.

FWIW, I tried building with that patch here (Debian GNU/Linux) and the
build doesn't have webp support.

    (image-type-available-p 'webp)
    => nil

bug#57420: 29.0.50; Failure configuring Emacs with animated WebP support

[Daniel Martín via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Stefan Kangas <stefankangas@gmail.com> writes:

> Daniel Martín via "Bug reports for GNU Emacs, the Swiss army knife of
> text editors" <bug-gnu-emacs@gnu.org> writes:
>
>> I checked that the built Emacs has WebP support.
>>
>> What do you think? I'd need an build system expert to verify that this
>> is TRT in GNU/Linux, Windows, or when pkg-config is not available.
>
> FWIW, I tried building with that patch here (Debian GNU/Linux) and the
> build doesn't have webp support.
>
>     (image-type-available-p 'webp)
>     => nil

Interesting.  Does this alternative patch work better?

diff --git a/configure.ac b/configure.ac
index 6ca3052ea3..afe71dbfa6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2777,7 +2777,7 @@ AC_DEFUN
 
       EMACS_CHECK_MODULES([WEBP], [$WEBP_MODULE])
       if test "$HAVE_WEBP" = "yes"; then
-        WEBP_LIBS="-lwebp -lwebpdemux"
+        WEBP_LIBS="$WEBP_LIBS -lwebpdemux"
       fi
       AC_SUBST([WEBP_CFLAGS])
       AC_SUBST([WEBP_LIBS])

bug#57420: 29.0.50; Failure configuring Emacs with animated WebP support

[Eli Zaretskii]

> Date: Thu, 25 Aug 2022 23:59:40 +0200
> From:  Daniel Martín via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> If WebP animated support requires -lwebpdemux, I think we could require
> the libwebpdemux module instead (part of the libwebp package), whose
> linker flags include "-lwebp -lwebpdemux".  The following patch fixes
> the compilation for me:
> 
> diff --git a/configure.ac b/configure.ac
> index 6ca3052ea3..4590ed3506 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -2773,12 +2773,9 @@ AC_DEFUN
>     || test "${HAVE_W32}" = "yes" || test "${HAVE_NS}" = "yes" \
>     || test "${HAVE_BE_APP}" = "yes" || test "${HAVE_PGTK}" = "yes"; then
>        WEBP_REQUIRED=0.6.0
> -      WEBP_MODULE="libwebp >= $WEBP_REQUIRED"
> +      WEBP_MODULE="libwebpdemux >= $WEBP_REQUIRED"
>  
>        EMACS_CHECK_MODULES([WEBP], [$WEBP_MODULE])
> -      if test "$HAVE_WEBP" = "yes"; then
> -        WEBP_LIBS="-lwebp -lwebpdemux"
> -      fi
>        AC_SUBST([WEBP_CFLAGS])
>        AC_SUBST([WEBP_LIBS])
>     fi
> 
> I checked that the built Emacs has WebP support.
> 
> What do you think?

LGTM, thanks.

bug#57420: 29.0.50; Failure configuring Emacs with animated WebP support

[Eli Zaretskii]

> From: Stefan Kangas <stefankangas@gmail.com>
> Date: Thu, 25 Aug 2022 22:50:24 +0000
> 
> Daniel Martín via "Bug reports for GNU Emacs, the Swiss army knife of
> text editors" <bug-gnu-emacs@gnu.org> writes:
> 
> > I checked that the built Emacs has WebP support.
> >
> > What do you think? I'd need an build system expert to verify that this
> > is TRT in GNU/Linux, Windows, or when pkg-config is not available.
> 
> FWIW, I tried building with that patch here (Debian GNU/Linux) and the
> build doesn't have webp support.
> 
>     (image-type-available-p 'webp)
>     => nil

Details, please.  Did the configure script decide that WebP is not
available?  If so, please show the relevant portion of config.log.
Also, what does the shell command below produce?

  $ pkg-config --libs "libwebpdemux >= 0.6.0"

bug#57420: 29.0.50; Failure configuring Emacs with animated WebP support

[Lars Ingebrigtsen]

Stefan Kangas <stefankangas@gmail.com> writes:

> FWIW, I tried building with that patch here (Debian GNU/Linux) and the
> build doesn't have webp support.
>
>     (image-type-available-p 'webp)
>     => nil

I tried the same on the current Ubuntu, and that call returns t in the
resulting Emacs.

bug#57420: 29.0.50; Failure configuring Emacs with animated WebP support

[Stefan Kangas]

Eli Zaretskii <eliz@gnu.org> writes:

> Details, please.  Did the configure script decide that WebP is not
> available?  If so, please show the relevant portion of config.log.
> Also, what does the shell command below produce?
>
>   $ pkg-config --libs "libwebpdemux >= 0.6.0"

False alarm: It turns out that I was by mistake running the Emacs
executable from the release branch.  I've rebuilt with Daniel's original
patch again, and it works as expected.

Sorry for the noise.

bug#57420: 29.0.50; Failure configuring Emacs with animated WebP support

[Eli Zaretskii]

> From: Stefan Kangas <stefankangas@gmail.com>
> Date: Fri, 26 Aug 2022 20:40:39 +0000
> Cc: mardani29@yahoo.es, 57420@debbugs.gnu.org
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Details, please.  Did the configure script decide that WebP is not
> > available?  If so, please show the relevant portion of config.log.
> > Also, what does the shell command below produce?
> >
> >   $ pkg-config --libs "libwebpdemux >= 0.6.0"
> 
> False alarm: It turns out that I was by mistake running the Emacs
> executable from the release branch.  I've rebuilt with Daniel's original
> patch again, and it works as expected.

Thanks.  So I think the original patch by Daniel should be installed.

bug#57420: 29.0.50; Failure configuring Emacs with animated WebP support

[Lars Ingebrigtsen]

Eli Zaretskii <eliz@gnu.org> writes:

> Thanks.  So I think the original patch by Daniel should be installed.

Yup; pushing the fix now.