[Buildroot] modem-manager: build issue

[Thomas Petazzoni <thomas.petazzoni@bootlin.com>]

Hello,

On Fri, 20 Apr 2018 00:23:13 -0300 (BRT), Carlos Santos wrote:

> There is a macro defined in build/libglib2-2.56.1/gobject/gobject.h which
> leads to the assignment errors:
> 
>   511 /* Make reference APIs type safe with macros */
>   512 #define g_object_ref(Obj)      ((__typeof__(Obj)) (g_object_ref) (Obj))
> 
> The problem can be easily reproduced with this sample code:
> 
> $ cat /tmp/test.c
> extern void *g_object_ref(void *);
> 
> /* Make reference APIs type safe with macros */
> #define g_object_ref(Obj)      ((__typeof__(Obj)) (g_object_ref) (Obj))
> 
> extern double *new_double(int *);
> 
> double *new_double(int *ip) {
>   double *dp;
>   dp = g_object_ref(ip);
>   return dp;
> }
> 
> $ gcc -Wall -Werror -c /tmp/test.c -o /tmp/test.o
> /tmp/test.c: In function ?new_context?:
> /tmp/test.c:19:13: error: assignment from incompatible pointer type [-Werror=incompatible-pointer-types]
>    ctx->self = g_object_ref(om);
>              ^
> cc1: all warnings being treated as errors

Thanks for the investigation!

> So in order to fix the build of ModemManager it would be necessary to either
> compile it without -Werror (with the risk of letting undesired assignments
> happen) or fix all the occurrences of the offending assignments.

If the patch to fix all the occurrences is small enough, we can do this
in Buildroot, and submit upstream.

If the patch is larger, then disabling -Werror is a better solution for
us, and report the issue upstream (or contribute the fix).

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com