GNU bug report logs - #74175
libtool mishandles some compiler flags when used with MSVC tools

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From: Ileana Dumitrescu <ileanadumitrescu95 <at> gmail.com>
To: "74175 <at> debbugs.gnu.org" <74175 <at> debbugs.gnu.org>
Cc: Kirill Makurin <maiddaisuki <at> outlook.com>
Subject: bug#74175: libtool mishandles some compiler flags when used with MSVC tools
Date: Thu, 5 Jun 2025 19:13:10 +0300

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On 05/06/2025 13:09, Kirill Makurin wrote:
> I am actually wrong. If we would pass -Wl and friends as is to clang.exe 
> it would handle them correctly by itself.
> 
> Note: clang.exe installed with Visual Studio uses link.exe, just like 
> cl.exe would.

Thank you for the updates. Is this an issue specifically with clang-cl?
I believe the issue is fixed with cl/cl.exe in development.

> What do you think about checking whether compiler defines _MSC_VER macro?

I do not have a strong opinion on this, so it could be added. Could you
submit a patch for review?

> - Kirill Makurin
> ------------------------------------------------------------------------
> *From:* bug-libtool-bounces+maiddaisuki=outlook.com <at> gnu.org <bug- 
> libtool-bounces+maiddaisuki=outlook.com <at> gnu.org> on behalf of Kirill 
> Makurin <maiddaisuki <at> outlook.com>
> *Sent:* Thursday, June 5, 2025 6:58 PM
> *To:* Ileana Dumitrescu <ileanadumitrescu95 <at> gmail.com>; 
> 74175 <at> debbugs.gnu.org <74175 <at> debbugs.gnu.org>
> *Subject:* bug#74175: libtool mishandles some compiler flags when used 
> with MSVC tools
> Hi Ileana,
> 
> The fix seems incomplete.
> 
> See attached file for `libtool --mode=link` invocation with clang-cl. 
> You may notice that the flag passed with -Wl is passed twice: once on 
> its own (just like it was with cl.exe with the bug) and once properly 
> with -Wl.
> 
> Do you think checking compiler's name is a good idea? AFAIK, all three 
> of cl.exe, clang-cl.exe and icl.exe (MSVC-like compilers handled by 
> Automake's `compile` wrapper) define _MSC_VER macro. If libtool does 
> check, it should be at least consistent with `compile` wrapper.

There are checks for compilers in libtool, like "cl* | icl*)" for
cc_basename when on a windows-like system. If libtool's configuration
when using clang-cl.exe is incorrect, these could be updated to avoid
clang-cl.exe or a new check could be added for the needed configuration.

> Maybe libtool could check during configuration whether compiler defines 
> this macro to decide how to pass linker flags? Since `compile` wrapper 
> should usually be involved, we need to just pass -Wl flags and friends 
> as is, `compile` takes care of them.
> 
> There is one problematic case though. If we would use clang.exe 
> installed with Visual Studio, this will not work. It defines _MSC_VER, 
> but it usus gcc-like command line options.

-- 
Ileana Dumitrescu

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