https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88270
Bug ID: 88270
Summary: -Wformat-XXX option for flagging %m
Product: gcc
Version: 8.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: eblake at redhat dot com
Target Milestone: ---
I was working porting a project originally written for Linux over to BSD
systems, and had to fix code that called printf("%m") to spell out longhand
printf("%s", strerror(errno)). Sadly, I couldn't find a -Wformat-FOO flag that
would have let the compiler spot these instances on my behalf.
At the same time, I found it a lot easier to write my own wrapper function [1]
that expanded %m in-place before passing things on to the real printf-family
functions (easy, since %m doesn't require parsing the rest of the format string
or rewriting the va_list argument), rather than manually expand all existing %m
in the code base, since most format strings in the code base already went
through a common wrapper function. Of course, my wrapper is given
__attribute__((printf...)), so that I can preserve compiler checking of
-Wformat. But in that case, while I'd want -Wformat-FOO to warn about %m in
native printf, I do NOT want it warning about %m passed to my wrapper. So the
attribute system may also need tweaking to make this sort of compiler-aided
portability flagging easier to implement.
[1] https://github.com/libguestfs/nbdkit/commit/1c230358462c3495330
