On 6 November 2014 13:59, Thierry Reding thierry.reding@gmail.com wrote:
On Thu, Nov 06, 2014 at 12:56:27PM +0100, Arnd Bergmann wrote:
On Thursday 06 November 2014 12:49:22 Thierry Reding wrote:
GCC complains about the format specifier being wrong. %zu/%zd are the correct specifiers for variables of type size_t/ssize_t, so wherever a size_t or ssize_t is used as parameter it should have a corresponding %zu or %zd specifier.
Why not just fix it properly instead of mucking about with the size_t typedef?
Yes, but where are %zu and %zd implemented in gcc? I've looked but couldn't find it. For all I can tell is that gcc's own interpretation of %z doesn't match its definition of __SIZE_TYPE__ when building for bare-metal.
I think the code you're looking for is gcc/c-family/c-format.c in function format_type_warning() (and its callers). Now my understanding of GCC internals is fairly limited, but what I think is happening is that the matching happens on the exact typedef, so even if size_t is typedef'd to unsigned int and the argument is of type unsigned int the check will still fail and cause the warning.
Yes, that is what it looks like.
Interestingly I can't seem to reproduce these warnings, neither with the native compiler on my system nor a 4.9.0 ARM cross-compiler. I've used the attached source file as a test case (derived from the code at line 1244 in drivers/regmap/regmap.c, which causes the warning in one of your
The mystery is that arm-linux-gnueabihf-gcc does not produce the warning, whereas Olof's arm-none-eabi-gcc does (built from the same source version, as far as we can tell)
logs). Can you verify that the same warning happens when you run your compiler on that? I've tried compiling with something like this:
$ gcc -Wall -Wextra -Wformat=2 -c test.cI don't think all of these are necessary, plain -Wformat /should/ be enough.
It's weird because both operands of the division are size_t, so I'm guessing the compiler looses the type information at some point.
I have tried this with the BE bare metal compiler I have on my system, and it did not produce a warning. (gcc-linaro-armeb-none-eabi-4.9-2014.06)