This is the mail archive of the
mailing list for the binutils project.
Dealing with multiple gas versions
- From: Ryan Mansfield <rmansfield at qnx dot com>
- To: <binutils at sourceware dot org>
- Date: Tue, 11 Oct 2011 15:28:20 -0400
- Subject: Dealing with multiple gas versions
Has there been any discussion of introducing a mechanism that allows
users to write code that is for specific version(s) of gas? Not
frequently but occasionally there are changes between versions where it
would be handy to write conditional code that could be assembled by
multiple versions of gas.
A recent example would be the change to separate the security extensions
from the base ARM v7-A architecture. E.g. prior to 2.21 gas would accept
the smc instruction if the .arch armv7-a was used or -march=armv7-a was
specified on the command line. Now it requires either +sec command line
option, or the .arch_extension sec inline. Unfortunately the
-march=armv7-a+sec option does not override the .arch option set by gcc,
so compiling code with inline asm containing the sec extensions with
-march=armv7-a -Wa,-march=armv7-a+sec is not possible unless the
.arch_extension sec is used. As .arch_extension is a recent addition as
well, it means the code needs to be written for the latest version of gas.
When we encounter a situation like this we usually end up encoding the
instruction to avoid the problem of having to target multiple versions
but it's far from ideal. If there was something like a builtin
expression for the version (e.g. something similar to __GNUC__ and
__GNUC_MINOR__) we could trigger off, it would be useful.
I apologize if this issue has been previously discussed and shot down
but I didn't find any particularly relevant in a quick search of the