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Exemple de mise à jour corrective : Mise à jour corrective de libpng pour fonctionner pour x64-uwp

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Journaux d’erreurs initiales

Tout d’abord, essayez de créer :

PS D:\src\vcpkg> vcpkg install libpng:x64-uwp --editable
Computing installation plan...
The following packages will be built and installed:
    libpng[core]:x64-uwp
Starting package 1/1: libpng:x64-uwp
Building package libpng[core]:x64-uwp...
-- Using cached D:/src/vcpkg/downloads/glennrp-libpng-v1.6.37.tar.gz
-- Extracting source D:/src/vcpkg/downloads/glennrp-libpng-v1.6.37.tar.gz
-- Using source at D:/src/vcpkg/buildtrees/libpng/src/v1.6.37-c993153cdf
-- Configuring x64-uwp
-- Building x64-uwp-rel
CMake Error at scripts/cmake/execute_required_process.cmake:14 (message):
  Command failed: C:/Program Files/CMake/bin/cmake.exe;--build;.;--config;Release

  Working Directory: D:/src/vcpkg/buildtrees/libpng/x64-uwp-rel

  See logs for more information:

      D:\src\vcpkg\buildtrees\libpng\build-x64-uwp-rel-out.log
      D:\src\vcpkg\buildtrees\libpng\build-x64-uwp-rel-err.log

Call Stack (most recent call first):
  scripts/cmake/vcpkg_build_cmake.cmake:3 (execute_required_process)
  ports/libpng/portfile.cmake:22 (vcpkg_build_cmake)
  scripts/ports.cmake:84 (include)


Error: build command failed

Ensuite, examinez les journaux ci-dessus (build-xxx-out.log et build-xxx-err.log).

// build-x64-uwp-rel-out.log
...
"D:\src\vcpkg\buildtrees\libpng\x64-uwp-rel\ALL_BUILD.vcxproj" (default target) (1) ->
"D:\src\vcpkg\buildtrees\libpng\x64-uwp-rel\png.vcxproj" (default target) (3) ->
(ClCompile target) -> 
  D:\src\vcpkg\buildtrees\libpng\src\v1.6.37-c993153cdf\pngerror.c(775): warning C4013: 'ExitProcess' undefined; assuming extern returning int [D:\src\vcpkg\buildtrees\libpng\x64-uwp-rel\png.vcxproj]


"D:\src\vcpkg\buildtrees\libpng\x64-uwp-rel\ALL_BUILD.vcxproj" (default target) (1) ->
"D:\src\vcpkg\buildtrees\libpng\x64-uwp-rel\png.vcxproj" (default target) (3) ->
(Link target) -> 
  pngerror.obj : error LNK2019: unresolved external symbol _ExitProcess referenced in function _png_longjmp [D:\src\vcpkg\buildtrees\libpng\x64-uwp-rel\png.vcxproj]
  D:\src\vcpkg\buildtrees\libpng\x64-uwp-rel\Release\libpng16.dll : fatal error LNK1120: 1 unresolved externals [D:\src\vcpkg\buildtrees\libpng\x64-uwp-rel\png.vcxproj]

    1 Warning(s)
    2 Error(s)

Time Elapsed 00:00:04.19

Identifier le code problématique

L’analyse de Microsoft Learn montre qu’elle ExitProcess n’est disponible que pour les applications de bureau. En outre, il est utile de voir le contexte environnant :

/* buildtrees\libpng\src\v1.6.37-c993153cdf\pngerror.c:769 */
    /* If control reaches this point, png_longjmp() must not return. The only
    * choice is to terminate the whole process (or maybe the thread); to do
    * this the ANSI-C abort() function is used unless a different method is
    * implemented by overriding the default configuration setting for
    * PNG_ABORT().
    */
    PNG_ABORT();

Une recherche récursive révèle PNG_ABORT la définition :

PS D:\src\vcpkg\buildtrees\libpng\src\v1.6.37-c993153cdf> findstr /snipl "PNG_ABORT" *
CHANGES:701:  Added PNG_SETJMP_SUPPORTED, PNG_SETJMP_NOT_SUPPORTED, and PNG_ABORT() macros
libpng-manual.txt:432:errors will result in a call to PNG_ABORT() which defaults to abort().
libpng-manual.txt:434:You can #define PNG_ABORT() to a function that does something
libpng-manual.txt:2753:errors will result in a call to PNG_ABORT() which defaults to abort().
libpng-manual.txt:2755:You can #define PNG_ABORT() to a function that does something
libpng-manual.txt:4226:PNG_NO_SETJMP, in which case it is handled via PNG_ABORT()),
libpng.3:942:errors will result in a call to PNG_ABORT() which defaults to abort().
libpng.3:944:You can #define PNG_ABORT() to a function that does something
libpng.3:3263:errors will result in a call to PNG_ABORT() which defaults to abort().
libpng.3:3265:You can #define PNG_ABORT() to a function that does something
libpng.3:4736:PNG_NO_SETJMP, in which case it is handled via PNG_ABORT()),
png.h:994: * will use it; otherwise it will call PNG_ABORT().  This function was
pngerror.c:773:    * PNG_ABORT().
pngerror.c:775:   PNG_ABORT();
pngpriv.h:459:#ifndef PNG_ABORT
pngpriv.h:461:#    define PNG_ABORT() ExitProcess(0)
pngpriv.h:463:#    define PNG_ABORT() abort()

Cela nous donne déjà de grands indices, mais la définition complète raconte l’histoire complète.

/* buildtrees\libpng\src\v1.6.37-c993153cdf\pngpriv.h:459 */
#ifndef PNG_ABORT
#  ifdef _WINDOWS_
#    define PNG_ABORT() ExitProcess(0)
#  else
#    define PNG_ABORT() abort()
#  endif
#endif

abort() est un appel CRT standard et certainement disponible dans UWP, donc nous devons simplement convaincre libpng d’être plus indépendant de la plateforme. Le moyen le plus simple et le plus fiable d’y parvenir consiste à corriger le code ; dans ce cas particulier, nous pourrions passer un indicateur de compilateur à remplacer PNG_ABORT , car il s’agit d’un en-tête privé, en général, il est plus fiable d’éviter d’ajouter des commutateurs de compilateur plus nécessaires lorsque cela est possible (en particulier lorsqu’il n’est pas déjà exposé en tant qu’option CMake).

Mise à jour corrective du code pour améliorer la compatibilité

Nous vous recommandons d’utiliser Git pour créer le fichier patch, car vous l’installerez déjà.

PS D:\src\vcpkg\buildtrees\libpng\src\v1.6.37-c993153cdf> git init .
Initialized empty Git repository in D:/src/vcpkg/buildtrees/libpng/src/v1.6.37-c993153cdf/.git/

PS D:\src\vcpkg\buildtrees\libpng\src\v1.6.37-c993153cdf> git add .
warning: LF will be replaced by CRLF in ANNOUNCE.
The file will have its original line endings in your working directory.
...

PS D:\src\vcpkg\buildtrees\libpng\src\v1.6.37-c993153cdf> git commit -m "temp"
[master (root-commit) 68f253f] temp
 422 files changed, 167717 insertions(+)
...

À présent, nous pouvons modifier pngpriv.h pour l’utiliser abort() partout.

/* buildtrees\libpng\src\v1.6.37-c993153cdf\pngpriv.h:459 */
#ifndef PNG_ABORT
#  define PNG_ABORT() abort()
#endif

La sortie d’un git diff correctif est déjà au format patch. Nous devons donc simplement enregistrer le correctif dans le ports/libpng répertoire.

PS buildtrees\libpng\src\v1.6.37-c993153cdf> git diff --ignore-space-at-eol | out-file -enc ascii ..\..\..\..\ports\libpng\use-abort-on-all-platforms.patch

Enfin, nous devons appliquer le correctif après l’extraction de la source.

# ports\libpng\portfile.cmake
...
vcpkg_extract_source_archive_ex(
  OUT_SOURCE_PATH SOURCE_PATH
  ARCHIVE ${ARCHIVE}
  PATCHES 
    "use-abort-on-all-platforms.patch"
)

vcpkg_cmake_configure(
...

Vérification

Pour être complètement sûr que cela fonctionne à partir de zéro, nous devons supprimer le package et le reconstruire :

PS D:\src\vcpkg> vcpkg remove libpng:x64-uwp
Package libpng:x64-uwp was successfully removed

Maintenant, nous essayons une nouvelle installation, à partir de zéro.

PS D:\src\vcpkg> vcpkg install libpng:x64-uwp
Computing installation plan...
The following packages will be built and installed:
    libpng[core]:x64-uwp
Starting package 1/1: libpng:x64-uwp
Building package libpng[core]:x64-uwp...
Could not locate cached archive: C:\Users\me\AppData\Local\vcpkg/archives\f4\f44b54f818f78b9a4ccd34b3666f566f94286850.zip
-- Using cached D:/src/vcpkg/downloads/glennrp-libpng-v1.6.37.tar.gz
-- Extracting source D:/src/vcpkg/downloads/glennrp-libpng-v1.6.37.tar.gz
-- Applying patch use_abort.patch
-- Applying patch cmake.patch
-- Applying patch pkgconfig.patch
-- Applying patch pkgconfig.2.patch
-- Using source at D:/src/vcpkg/buildtrees/libpng/src/v1.6.37-10db9f58e4.clean
-- Configuring x64-uwp
-- Building x64-uwp-dbg
-- Building x64-uwp-rel
-- Fixing pkgconfig file: D:/src/vcpkg/packages/libpng_x64-uwp/lib/pkgconfig/libpng.pc
-- Fixing pkgconfig file: D:/src/vcpkg/packages/libpng_x64-uwp/lib/pkgconfig/libpng16.pc
-- Fixing pkgconfig file: D:/src/vcpkg/packages/libpng_x64-uwp/debug/lib/pkgconfig/libpng.pc
-- Fixing pkgconfig file: D:/src/vcpkg/packages/libpng_x64-uwp/debug/lib/pkgconfig/libpng16.pc
-- Installing: D:/src/vcpkg/packages/libpng_x64-uwp/share/libpng/copyright
-- Performing post-build validation
-- Performing post-build validation done
Stored binary cache: C:\Users\me\AppData\Local\vcpkg/archives\f4\f44b54f818f78b9a4ccd34b3666f566f94286850.zip
Building package libpng[core]:x64-uwp... done
Installing package libpng[core]:x64-uwp...
Installing package libpng[core]:x64-uwp... done
Elapsed time for package libpng:x64-uwp: 11.94 s

Total elapsed time: 11.95 s

The package libpng:x64-uwp provides CMake targets:

    find_package(libpng CONFIG REQUIRED)
    target_link_libraries(main PRIVATE png)

Enfin, pour valider et publier entièrement les modifications, nous devons faire passer la version du port dans vcpkg.json, et ajouter le fichier patch au contrôle de code source, puis effectuer une demande de tirage ( Pull Request) !

{
  "name": "libpng",
  "version": "1.6.37",
  "port-version": 1,
  "dependencies": [
    "zlib"
  ]
}