c/2678: gcc/g++ should stick compilation options into the .o file

[Ronald F. Guilmette]

The following reply was made to PR c/2678; it has been noted by GNATS.

From: "Ronald F. Guilmette" <rfg@monkeys.com>
To: Phil Edwards <pedwards@disaster.jaj.com>
Cc: gcc-gnats@gcc.gnu.org
Subject: Re: c/2678: gcc/g++ should stick compilation options into the .o file 
Date: Mon, 30 Apr 2001 02:09:48 -0700

 In message <20010429214104.A29946@disaster.jaj.com>, you wrote:
 
 >After some sleep, I've concluded that my original idea of using the
 >print_switch_values routine might be stupid.  I don't think people would like
 >
 >    options passed:  -iprefix -D__GNUC__=3 -D__GNUC_MINOR__=1
 >    -D__GNUC_PATCHLEVEL__=0 -D__ELF__ -Dunix -Dlinux -D__ELF__ -D__unix__
 >    -D__linux__ -D__unix -D__linux -Asystem=posix -D__STDC_HOSTED__=1
 >    -Acpu=i386 -Amachine=i386 -Di386 -D__i386 -D__i386__ -D__tune_i686__
 >    -D__tune_pentiumpro__ -D__GNUG__=3 -D_GNU_SOURCE -D__DEPRECATED
 >    -D__EXCEPTIONS -D__GXX_ABI_VERSION=100
 >    options enabled:  -fpeephole -ffunction-cse -fkeep-static-consts
 >    -fpcc-struct-return -fgcse-lm -fgcse-sm -fsched-interblock -fsched-spec
 >    -fbranch-count-reg -fexceptions -fcommon -fgnu-linker -fargument-alias
 >    -fident -fmath-errno -ftrapping-math -m80387 -mhard-float
 >    -mno-soft-float -mieee-fp -mfp-ret-in-387
 >
 >showing up in their object files, for example.  (Or do you?)
 
 Yes, it would be perfectly OK to put that all into a .comment or .note
 section.  Those sections DO NOT get loaded into main memory at run time,
 and if necessary, `strip' and be used to remove them after the .o is built.
 
 >The kicker is that the driver doesn't pass down the set of command-line
 >options directly to the compiler.  It does some translations on them,
 >and then adds a bunch of defaults, and then passes /all/ of that down.
 
 That might still be OK.  It's better than not having the info at all!
 
 >(Side note:  the "options enabled" block are everything that's on by
 >default, as modified by the "options passed".  If you really wanted to
 >re-create the compilation environment for a particular file, you'd need
 >to use all of those.  The defaults might have changed.)
 
 Good point.
 
 >The compiler does have available a save_argv and save_argc, but that's how
 >the "options passed" block is constructed in the first place.  We don't
 >have any obvious way of distinguishing which options the user passed from
 >the default ones added by the specs file.
 
 I don't believe that it is important to draw that distinction anyway.