When linking against libpng/zlib on Windows, use upstream lib names.

anntzer · anntzer · commit 74b8a16dfb51 · 2019-01-02T20:05:57.000+01:00
See changelog for details.
diff --git a/.appveyor.yml b/.appveyor.yml
@@ -76,8 +76,8 @@ install:
   # Let the install prefer the static builds of the libs
   - set LIBRARY_LIB=%CONDA_PREFIX%\Library\lib
   - mkdir lib || cmd /c "exit /b 0"
-  - copy /y %LIBRARY_LIB%\zlibstatic.lib lib\z.lib
-  - copy /y %LIBRARY_LIB%\libpng_static.lib lib\png.lib
+  - copy /y %LIBRARY_LIB%\zlibstatic.lib lib\zlib.lib
+  - copy /y %LIBRARY_LIB%\libpng_static.lib lib\libpng.lib
   # These z.lib / png.lib are not static versions but files which end up as
   # dependencies to the dll file. This is fine for the conda build, but not here
   # and for the wheels
diff --git a/build_alllocal.cmd b/build_alllocal.cmd
@@ -20,8 +20,8 @@ IF NOT DEFINED CONDA_PREFIX (
 :: copy the libs which have "wrong" names
 set LIBRARY_LIB=%CONDA_PREFIX%\Library\lib
 mkdir lib || cmd /c "exit /b 0"
-copy %LIBRARY_LIB%\zlibstatic.lib lib\z.lib
-copy %LIBRARY_LIB%\libpng_static.lib lib\png.lib
+copy %LIBRARY_LIB%\zlibstatic.lib lib\zlib.lib
+copy %LIBRARY_LIB%\libpng_static.lib lib\libpng.lib
 
 :: Make the header files and the rest of the static libs available during the build
 :: CONDA_PREFIX is a env variable which is set to the currently active environment path
diff --git a/doc/api/next_api_changes/2019-01-02-AL.rst b/doc/api/next_api_changes/2019-01-02-AL.rst
@@ -0,0 +1,19 @@
+Changes to the Windows build
+````````````````````````````
+
+Previously, when building the :mod:`matplotlib._png` extension, the build
+script would add "png" and "z" to the extensions ``.libraries`` attribute (if
+pkg-config information is not available, which is in particular the case on
+Windows).
+
+In particular, this implies that the Windows build would look up files named
+``png.lib`` and ``z.lib``; but neither libpng upstream nor zlib upstream
+provides these files by default.  (On Linux, this would look up ``libpng.so``
+and ``libz.so``, which are indeed standard names.)
+
+Instead, on Windows, we now look up ``libpng16.lib`` and ``zlib.lib``, which
+*are* the upstream names for the shared libraries (as of libpng 1.6.x).
+
+For a statically-linked build, the upstream names are ``libpng16_static.lib``
+and ``zlibstatic.lib``; one still needs to manually rename them if such a build
+is desired.
diff --git a/setupext.py b/setupext.py
@@ -1022,7 +1022,14 @@ def get_extension(self):
             ]
         ext = make_extension('matplotlib._png', sources)
         pkg_config.setup_extension(
-            ext, 'libpng', default_libraries=['png', 'z'],
+            ext, 'libpng',
+            default_libraries=(
+                ['png', 'z'] if os.name == 'posix' else
+                # libpng upstream names their lib libpng16.lib, not png.lib.
+                # zlib upstream names their lib zlib.lib, not z.lib.
+                ['libpng16', 'zlib'] if os.name == 'nt' else
+                []
+            ),
             alt_exec='libpng-config --ldflags')
         Numpy().add_flags(ext)
         return ext
