On Thu, Oct 20, 2016 at 7:53 PM, Jonathan Wakely <jwakely.gcc@xxxxxxxxx> wrote: > On 20 October 2016 at 18:42, john smith wrote: >> We use the same cross-compiler on two Linux machines: machine A and >> machine B. It produces some warnings on machine A but not on machine >> B when used to compile the same file and with the same set of options >> (specifically we use -Wall and -Wextra). We are absolutely sure that >> it's the same compiler - it's in the same version and has the same >> md5sum on both machines. However, these 2 Linux machines differ - A >> is x32 Ubuntu, B is x64 bit Slackware. I checked all environment > > Do you really mean x32, as in https://en.wikipedia.org/wiki/X32_ABI ? > Or do you mean you mean x86 aka IA-32? Sorry, I meant x86. > Are both compilers producing 32-bit output? Both producing 64-bit > output? One 32-bit and one 64-bit? > > That could make all the difference, compiling printf("%lu", > sizeof(1)); will warn for i686 and not for x86_64, for example. They both produce output for ARM 32-bit. They are the same, and have been configured the same by the vendor. >> variables on both machines and didn't find anything suspicious - no >> CFLAGS, CC or something related to compilation at all. The compiler >> in question behaves the same way when invoked from Makefile and when >> invoked directly from the command line on both machines. >> >> Is this possible that due to some local differences in >> libc/libgcc/whatnot GCC emits warnings on machine A but not on machine >> B? > > Yes. Of course. If a header in /usr/include has a #warning in it on > one machine and not in the other it's going to warn on one machine and > not on the other. That's a silly example, but t here are loads of > things that could cause it. Since it's a cross-compiler do headers in /usr/include matter? >> What else can I check to learn what's the culprit here? > > All you've said is "I checked everything" and not told us anything useful. > > What's the warning? What does the code look like that triggers it? The warnings are: warning: control reaches end of non-void function [-Wreturn-type] and: warning: unused variable 'i' [-Wunused-variable] The code is something like this (I cannot show the real code, sorry): #include <stdio.h> #include <stdlib.h> int foo(void) {} int main(void) { foo(); int i = 10; return EXIT_SUCCESS; } -- <wempwer@xxxxxxxxx>
