Re: -Wlto-type-mismatch warning in error()

[Bruno Haible]

Gavin Smith wrote:
> I expect it is not a gnulib problem.  install-info/install-info.c declares
> a function called "error" which appears to clash with a function from glibc.
> ... The "error" module is brought in by "xalloc" (which we
> ask for explicitly).

Yes, I think the problems already exists without use of Gnulib, as it's
a conflict between install-info.c and glibc. But with the Gnulib 'error'
module, the problem becomes bigger.

Namely, see:

$ nm --dynamic /lib/x86_64-linux-gnu/libc.so.6 | grep ' error'
00000000001214e0 W error@@GLIBC_2.2.5
0000000000121700 W error_at_line@@GLIBC_2.2.5
0000000000221484 B error_message_count@@GLIBC_2.2.5
0000000000221480 B error_one_per_line@@GLIBC_2.2.5
0000000000221488 B error_print_progname@@GLIBC_2.2.5

glibc exports 'error' as a weak symbol. This means, without use of Gnulib,
the symbol from install-info.c overrides the one from glibc, and there is
a problem if and only if the 'install-info' program links dynamically
(or loads via 'dlopen') a shared library which happens to use error()
and expects the semantics from glibc.

Whereas with the Gnulib 'error' module, there is a conflict between the
two global function definitions (with 'T' linkage) in install-info.c and
in error.c *always*.

> The simplest way to fix this problem would probably be to rename the "error"
> function in install-info.c.

Yes, or make it 'static' (like Arsen suggested).

Bruno