bug#52276: 28.0.50; [PATCH] Scuttle compiler warning in image.c

bug#52276: 28.0.50; [PATCH] Scuttle compiler warning in image.c

[dick]

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From 2f1a3475910bfea5d0c0ead874a238db3ecbf3ad Mon Sep 17 00:00:00 2001
From: dickmao <dick.r.chiang@gmail.com>
Date: Sat, 4 Dec 2021 07:32:00 -0500
Subject: [PATCH] Scuttle a compiler warning under --enable-checking

* src/image.c (webp_load): Scuttle compiler warning.
---
 src/image.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/image.c b/src/image.c
index b85c405487..709abc21aa 100644
--- a/src/image.c
+++ b/src/image.c
@@ -8970,7 +8970,7 @@ webp_load (struct frame *f, struct image *img)
 {
   ptrdiff_t size = 0;
   uint8_t *contents;
-  Lisp_Object file;
+  Lisp_Object file = Qnil;
 
   /* Open the WebP file.  */
   Lisp_Object specified_file = image_spec_value (img->spec, QCfile, NULL);
@@ -9007,7 +9007,7 @@ webp_load (struct frame *f, struct image *img)
   /* Validate the WebP image header.  */
   if (!WebPGetInfo (contents, size, NULL, NULL))
     {
-      if (NILP (specified_data))
+      if (! NILP (file))
 	image_error ("Not a WebP file: `%s'", file);
       else
 	image_error ("Invalid header in WebP image data");
@@ -9030,7 +9030,7 @@ webp_load (struct frame *f, struct image *img)
     case VP8_STATUS_USER_ABORT:
     default:
       /* Error out in all other cases.  */
-      if (NILP (specified_data))
+      if (! NILP (file))
 	image_error ("Error when interpreting WebP image data: `%s'", file);
       else
 	image_error ("Error when interpreting WebP image data");
-- 
2.26.2


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In Commercial Emacs 28.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.22.30, cairo version 1.15.10)
 of 2021-12-04 built on dick
Repository revision: 496cf662a994ab288a4fb75f70ceb053af27a2a9
Repository branch: dev
Windowing system distributor 'The X.Org Foundation', version 11.0.11906000
System Description: Ubuntu 18.04.4 LTS

Configured using:
 'configure --prefix=/home/dick/.local --enable-checking
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bug#52276: 28.0.50; [PATCH] Scuttle compiler warning in image.c

[Lars Ingebrigtsen]

dick <dick.r.chiang@gmail.com> writes:

> * src/image.c (webp_load): Scuttle compiler warning.

[...]

> +  Lisp_Object file = Qnil;

What gcc version gives you a warning?  I'm not seeing a warning in

gcc (Debian 10.2.1-6) 10.2.1 20210110

or

gcc (Debian 11.2.0-10) 11.2.0

and the warning seems spurious to me.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#52276: 28.0.50; [PATCH] Scuttle compiler warning in image.c

[dick]

I only recently discovered --enable-checking.  And here I thought all my
easserts were actually in force.

>>>>> Lars Ingebrigtsen <larsi@gnus.org> writes:

> dick <dick.r.chiang@gmail.com> writes:
>> * src/image.c (webp_load): Scuttle compiler warning.

> [...]

>> +  Lisp_Object file = Qnil;

> What gcc version gives you a warning?  I'm not seeing a warning in

> gcc (Debian 10.2.1-6) 10.2.1 20210110

> or

> gcc (Debian 11.2.0-10) 11.2.0

> and the warning seems spurious to me.

bug#52276: 28.0.50; [PATCH] Scuttle compiler warning in image.c

[Lars Ingebrigtsen]

dick <dick.r.chiang@gmail.com> writes:

> I only recently discovered --enable-checking.  And here I thought all my
> easserts were actually in force.

[...]

>> What gcc version gives you a warning?

You didn't answer my question, but:

> System Description: Ubuntu 18.04.4 LTS

So I guess it's an old gcc version.

Looking at the function in question again, the warning seems spurious.
We do cater to compiler bugs, but not for older gcc versions (which I
have to guess you're using, since you didn't answer), so I'm closing
this bug report.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#52276: 28.0.50; [PATCH] Scuttle compiler warning in image.c

[dick]

> You didn't answer my question, but:

My bad: 

gcc-10 (Ubuntu 10.3.0-1ubuntu1~18.04~1) 10.3.0

I dodged your question with some blather about "--enable-checking"
because the warning doesn't manifest without that configure switch.

bug#52276: 28.0.50; [PATCH] Scuttle compiler warning in image.c

[Lars Ingebrigtsen]

dick <dick.r.chiang@gmail.com> writes:

> My bad: 
>
> gcc-10 (Ubuntu 10.3.0-1ubuntu1~18.04~1) 10.3.0

Ah, I see...  Ah!  I didn't see the warning on Debian stable because I
didn't have libwebp installed there.  And the compiler bug is apparently
gone in gcc 11.

But since the warning is manifesting in the current release of a major
distribution, I think adding a workaround is in order, and I'm applying
your patch to Emacs 29.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no