Re: the same gcc binary emits warnings on one machine but not on another

[Jeff Law <law at redhat dot com>]

On 10/20/2016 11:42 AM, 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
> 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?  What else can I check to learn what's the culprit here?
I would suggest checking the contents of the pre-processed files.  Most 
likely you've got different headers and the difference would show up in 
the preprocessed output.

Adding "-save-temps" to the compilation line will generate the 
preprocessed .i files.  Compare those.

jeff