[FFmpeg-devel] [PATCH] configure: fix static library suffix for MSVC builds

[Practice2001 via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

MSVC static builds currently always use ".a" for static library suffixes
(e.g. libavcodec.a, libavformat.a). This causes failures when linking
with Visual Studio, which expects ".lib" static libraries.

This patch adjusts configure so that when --toolchain=msvc is used,
LIBSUF is correctly set to ".lib" instead of the Unix default ".a".

This fixes linking with MSVC and Visual Studio-based build systems.

---

Environment:
 - Windows 10
 - MSYS2 (mingw64)
 - Visual Studio 2019 / 2022
 - NASM installed
 - MSVC toolchain selected

Commands:

    ./configure --toolchain=msvc --enable-static --disable-shared
    make

Resulting static libraries incorrectly have ".a" suffix, e.g.:

    libavcodec.a
    libavformat.a
    libavutil.a

Linking test program with MSVC:

    cl test_ffmpeg.c /I C:\ffmpeg-test-install\include ^
        /link /LIBPATH:C:\ffmpeg-test-install\lib avcodec.lib avformat.lib avutil.lib

Error:

    LINK : fatal error LNK1181: cannot open input file 'avcodec.lib'

---

Verification of the fix:

After applying this patch and rebuilding:

Generated static libraries:

    avcodec.lib
    avformat.lib
    avutil.lib

Test program build script (build_test.bat):

    cl test_ffmpeg.c ^
        /I C:\ffmpeg-test-install\include ^
        /link /LIBPATH:C:\ffmpeg-test-install\lib ^
        avcodec.lib avformat.lib avutil.lib

Output:
	D:\ffmpeg\temp>.\buid_test.bat
	Microsoft (R) C/C++ Optimizing Compiler Version 19.50.35718 for x64
	Copyright (C) Microsoft Corporation.  All rights reserved.

	test_ffmpeg.c
	Microsoft (R) Incremental Linker Version 14.50.35718.0
	Copyright (C) Microsoft Corporation.  All rights reserved.

	/out:test_ffmpeg.exe
	/LIBPATH:C:\ffmpeg-test-install\lib
	avcodec.lib
	avformat.lib
	avutil.lib
	/OUT:test.exe
	test_ffmpeg.obj

	=== BUILD SUCCESS ===
	Running test...
	FFmpeg avcodec version: 4068196
	FFmpeg avformat version: 4064871
	FFmpeg avutil version: 3936868

This confirms MSVC accepts the .lib suffix and the libraries function
correctly.

---
 configure | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/configure b/configure
index 47f9b31439..596d66ce53 100755
--- a/configure
+++ b/configure
@@ -6067,7 +6067,7 @@ case $target_os in
     win32|win64)
         disable symver
         LIBPREF=""
-		LIBSUF=".lib"
+        LIBSUF=".lib"
         if enabled shared; then
             # Cannot build both shared and static libs with MSVC or icl.
             disable static
-- 
2.34.1

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