Bug 23685

Summary:	[asyncns] Gabble fails to build with pedantic gcc
Product:	Telepathy	Reporter:	Pierre-Luc Beaudoin <pierre-luc>
Component:	gabble	Assignee:	Guillaume Desmottes <guillaume.desmottes>
Status:	RESOLVED FIXED	QA Contact:	Telepathy bugs list <telepathy-bugs>
Severity:	major
Priority:	high	CC:	84yelo3, biru.ionut, lennart
Version:	unspecified	Keywords:	patch
Hardware:	Other
OS:	All
URL:	http://git.collabora.co.uk/?p=user/cassidy/telepathy-gabble;a=shortlog;h=refs/heads/build
Whiteboard:
i915 platform:		i915 features:

Description Pierre-Luc Beaudoin 2009-09-03 06:26:09 UTC

Building telepathy-gabble on Ubuntu Karmic Koala:

I'll let Lennart know about this bug.

libtool: compile:  gcc -std=gnu99 -DHAVE_CONFIG_H -I. -I../.. -Wall -Werror -Wextra -Wno-missing-field-initializers -Wno-unused-parameter -Wdeclaration-after-statement -Wshadow -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -pthread -I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include -g -O2 -MT asyncns.lo -MD -MP -MF .deps/asyncns.Tpo -c asyncns.c  -fPIC -DPIC -o .libs/asyncns.o
cc1: warnings being treated as errors
asyncns.c: In function ‘process_worker’:
asyncns.c:526: error: dereferencing pointer ‘ai_req’ does break strict-aliasing rules
asyncns.c:526: error: dereferencing pointer ‘ai_req’ does break strict-aliasing rules
asyncns.c:529: error: dereferencing pointer ‘ai_req’ does break strict-aliasing rules
asyncns.c:530: error: dereferencing pointer ‘ai_req’ does break strict-aliasing rules
asyncns.c:531: error: dereferencing pointer ‘ai_req’ does break strict-aliasing rules
asyncns.c:532: error: dereferencing pointer ‘ai_req’ does break strict-aliasing rules
asyncns.c:534: error: dereferencing pointer ‘ai_req’ does break strict-aliasing rules
asyncns.c:535: error: dereferencing pointer ‘ai_req’ does break strict-aliasing rules
asyncns.c:535: error: dereferencing pointer ‘ai_req’ does break strict-aliasing rules
asyncns.c:538: error: dereferencing pointer ‘ai_req’ does break strict-aliasing rules
asyncns.c:521: note: initialized from here
asyncns.c:552: error: dereferencing pointer ‘ni_req’ does break strict-aliasing rules
asyncns.c:554: error: dereferencing pointer ‘ni_req’ does break strict-aliasing rules
asyncns.c:559: error: dereferencing pointer ‘ni_req’ does break strict-aliasing rules
asyncns.c:558: error: dereferencing pointer ‘ni_req’ does break strict-aliasing rules
asyncns.c:558: error: dereferencing pointer ‘ni_req’ does break strict-aliasing rules
asyncns.c:557: error: dereferencing pointer ‘ni_req’ does break strict-aliasing rules
asyncns.c:557: error: dereferencing pointer ‘ni_req’ does break strict-aliasing rules
asyncns.c:556: error: dereferencing pointer ‘ni_req’ does break strict-aliasing rules
asyncns.c:563: error: dereferencing pointer ‘ni_req’ does break strict-aliasing rules
asyncns.c:562: error: dereferencing pointer ‘ni_req’ does break strict-aliasing rules
asyncns.c:547: note: initialized from here
asyncns.c:575: error: dereferencing pointer ‘res_req’ does break strict-aliasing rules
asyncns.c:580: error: dereferencing pointer ‘res_req’ does break strict-aliasing rules
asyncns.c:580: error: dereferencing pointer ‘res_req’ does break strict-aliasing rules
asyncns.c:582: error: dereferencing pointer ‘res_req’ does break strict-aliasing rules
asyncns.c:582: error: dereferencing pointer ‘res_req’ does break strict-aliasing rules
asyncns.c:571: note: initialized from here
make[4]: *** [asyncns.lo] Error 1

Comment 1 Lennart Poettering 2009-09-03 09:40:38 UTC

You shouldn't use -Werror when building this. The code in asyncns.c breaks C99 strict aliasing ruless.

(BTW, glib now has an async dns module that embedds libasyncns. Might be a good idea to port your code over to that instead of using libasyncns directly)

Comment 2 Guillaume Desmottes 2009-09-14 03:27:30 UTC

http://git.collabora.co.uk/?p=user/cassidy/telepathy-gabble;a=shortlog;h=refs/heads/gibber-error
removes ERROR_CFLAGS when building Gibber.

Comment 3 Guillaume Desmottes 2009-09-14 03:31:49 UTC

I opened bug #23920 about the GResolver switch. I'd prefer to quickly fix this issue without having to block on it as I currently can't build Gabble.

Comment 4 Simon McVittie 2009-09-14 04:56:52 UTC

(In reply to comment #1)
> You shouldn't use -Werror when building this. The code in asyncns.c breaks C99
> strict aliasing rules.

Shouldn't it either not do that, or be documented as "must be compiled with -fno-strict-aliasing", given that AIUI the gcc warnings basically mean "I think I'm applying unsafe optimizations to your code"?

Comment 5 Lennart Poettering 2009-09-14 06:26:53 UTC

(In reply to comment #4)
> (In reply to comment #1)
> > You shouldn't use -Werror when building this. The code in asyncns.c breaks C99
> > strict aliasing rules.
> 
> Shouldn't it either not do that, or be documented as "must be compiled with
> -fno-strict-aliasing", given that AIUI the gcc warnings basically mean "I think
> I'm applying unsafe optimizations to your code"?

Yes, of course, I should fix this. It is on my todo list already, just haven't found the time yet.

I think the meaning of the warning is actually "I am not applying optimizations here because your code stinks", though... ;-) But tbh I neer really verified my interpretation of this.

Comment 6 Simon McVittie 2009-09-14 12:23:24 UTC

*** Bug 23567 has been marked as a duplicate of this bug. ***

Comment 7 Simon McVittie 2009-09-14 12:23:31 UTC

*** Bug 22413 has been marked as a duplicate of this bug. ***

Comment 8 Simon McVittie 2009-09-14 12:24:56 UTC

Guillaume, could you fix this, either by improving asyncns.c or by compiling it with -fno-strict-aliasing?

Comment 9 Guillaume Desmottes 2009-09-16 03:00:14 UTC

done:
http://git.collabora.co.uk/?p=user/cassidy/telepathy-gabble;a=shortlog;h=refs/heads/build

Comment 10 Guillaume Desmottes 2009-09-16 03:21:27 UTC

Fixed in master. Will be in 0.9.0.

Comment 11 Guillaume Desmottes 2009-09-16 04:32:17 UTC

Fixed in the 0.8 branch as well

Comment 12 Lennart Poettering 2009-10-14 18:34:13 UTC

A small followup:

Upstream libasyncns in git now compiles cleanly with -Wstrict-aliasing. Will release that as 0.8 shortly.

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