URL:
<http://gna.org/bugs/?16249>
Summary: Can't build trunk with -Werror: "format not a
string literal and no format arguments"
Project: Freeciv
Submitted by: jtn
Submitted on: Saturday 07/10/10 at 22:50
Category: None
Severity: 4 - Important
Priority: 5 - Normal
Status: None
Assigned to: None
Originator Email:
Open/Closed: Open
Release: trunk r17569
Discussion Lock: Any
Operating System: GNU/Linux
Planned Release: 2.3.0
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Details:
This has come in some time in the last few days:
libtool: compile: gcc [...] -c savegame2.c -o savegame2.o
cc1: warnings being treated as errors
savegame2.c: In function ‘sg_load_game’:
savegame2.c:1742: error: format not a string literal and no format arguments
savegame2.c: In function ‘sg_load_random’:
savegame2.c:1870: error: format not a string literal and no format arguments
savegame2.c:1872: error: format not a string literal and no format arguments
savegame2.c:1874: error: format not a string literal and no format arguments
savegame2.c:1879: error: format not a string literal and no format arguments
[...and many more the same...]
(GCC 4.3.3 on Ubuntu Jaunty.)
A bit of digging on the first one at least shows it's complaining about
sg_failure_ret(), which boils down to do_log(), which has fancy printf
attributes ("fc__attribute((__format__ (__printf__, 6, 7)))").
Somewhere in there it boils down to "log_sg(secfile_error())".
Have run out of time to fix it myself, but: This site
<http://bobthegnome.blogspot.com/2009/07/format-not-string-literal-and-no-format.html>
suggests the fix. It's complaining about format-string vulnerabilities because
it can't vet that what secfile_error() returns doesn't have a % in it. The fix
should be simple: change the various invocations so we end up with (..., "%s",
secfile_error()).
In passing, I note there's a lot of usage in Freeciv of patterns like:
#define foo(format, ...) bar(thingy, format, ##__VA_ARGS__)
The ## is a GNU extension
<http://gcc.gnu.org/onlinedocs/cpp/Variadic-Macros.html> so that if you do
something like 'foo("Hello")' (no extra arguments), the comma is swallowed --
apparently standard C99 has no way of doing this. This means Freeciv relies on
a GNU extension. I can't remember, is that bad? If so I dunno what we can do
about it.
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