Christophe LYON wrote:
Hi Andrew,
Thanks for your answer.
The documentation only mentions the size of int and pointer types.
The gcc documentation talks only about gcc; you're asking about the
system linker.
I did not mean that.
If I compile a.c with "gcc-x.x.x (32 bits)" on a Pentium 4 machine,
and with "gcc-x.x.x (64 bits) -m32" on an Opteron, am I guaranteed
that both a.o will have the same contents?
Any risk that the file compiled on Opteron contains Opteron-only
instructions for instance? Or references only 64 bits variants of some
system structures?
If you use -m32 it will be x86_32 code, sections, etc. You should be
able to link it with a 32-bit binutils just fine (provided your on the
same revision of GCC, e.g. don't mix a 32-bit GCC 3.2 with a 64-bit GCC
4.3).
You won't be guaranteed to get the same object code (byte for byte)
unless you have the exact same configuration for GCC and revision.
If I compile a.c with "gcc-x.x.x (32 bits)" on a Pentium 4 machine,
and b.c with "gcc-x.x.x (64 bits) -m32" on an Opteron, I need to be
able to link a.o and b.o together and that the result is actually
meaningful on a Pentium 4.
Linking should be no problem provided they're the same revision. Also
helps to build your 64-bit GCC with multi-lib enabled.
Tom
