Re: [PATCH 4/4] Makefile: Don't pass $(ALL_CFLAGS) to the linker

From: Jonathan Nieder <jrnieder@gmail.com>
Date: Jun 26, 2010, 18:19 UTC
Message-ID: <20100626181945.GA13070@burratino>
In-Reply-To: <4C264019.6030408@ramsay1.demon.co.uk>

Ramsay Jones wrote:

Show 11 quoted lines

> I thought that the general scheme was something like:
> 
>     - LDFLAGS is for options which only affects the operation of
>       the linker (e.g. -L).
>     - CPPFLAGS is for options which only affects the operation of
>       the C pre-processor (e.g. -I, -D, -U)
>     - CFLAGS is for options which only affects the operation of
>       the compiler proper.
>
> If an option affects multiple phases, then (one option) is to include
> it into each of the above macros to which it applies.

That does make sense. Perhaps “traditionally” was not the right word; I was just looking at common practice. I’ve just never seen -O put into LDFLAGS, for example, and I think most people would expect setting CFLAGS=-O0 to affect the linker, too.

> Jonathan Nieder wrote:

>> I realize that the Makefile does not currently use the terms this way:
>> making it consistent would require
>> 
>>  . s/BASIC_CFLAGS/BASIC_CPPFLAGS/, except that the

[etc]

Show 5 quoted lines

>> 
>> What do you think?
>
> I think I am missing something, since I don't see how this relates to
> my patch!

I suspect the problem comes from my unfamiliarity with MSVC.

By analogy with GCC, I assumed that any parameter is intended for the preprocessor, the linker, or the frontend/both. In other words, I was assuming flags for the compiler proper can be safely passed to the linker, and that /Zi must be for the preprocessor-using stages only. CFLAGS tends to contain front-end arguments used for all stages of translation.

What does /Zi do?  Searching online reveals:

 - it means “enable debugging information”
 - weakly implies /debug for the linker
 - overrides /Z7 and /Zd, and is overridden by them
 - is incompatible with /MP
 - is among the prerequisites for /dlp and for /Gm

Maybe clink.pl should use “cl.exe /link” instead of “link.exe” and this problem would go away.