Modules: Guard calls to pkg_check_modules

Before calling pkg_check_modules, modules must check PKG_CONFIG_FOUND.
When FindPkgConfig.cmake is loaded, pkg_check_modules is always defined
regardless of pkg-config being present. However, the whole module might
be disabled on user request with CMAKE_DISABLE_FIND_PACKAGE_PkgConfig.
This must not break Find modules which just look for a hint or similar.

Modules/FindBLAS.cmake

@@ -293,12 +293,14 @@ if(BLA_PREFER_PKGCONFIG)
     set(BLA_PKGCONFIG_BLAS "blas")
   endif()
   find_package(PkgConfig QUIET)
-  pkg_check_modules(PKGC_BLAS QUIET ${BLA_PKGCONFIG_BLAS})
+  if(PKG_CONFIG_FOUND)
-  if(PKGC_BLAS_FOUND)
+    pkg_check_modules(PKGC_BLAS QUIET ${BLA_PKGCONFIG_BLAS})
-    set(BLAS_FOUND ${PKGC_BLAS_FOUND})
+    if(PKGC_BLAS_FOUND)
-    set(BLAS_LIBRARIES "${PKGC_BLAS_LINK_LIBRARIES}")
+      set(BLAS_FOUND ${PKGC_BLAS_FOUND})
-    _add_blas_target()
+      set(BLAS_LIBRARIES "${PKGC_BLAS_LINK_LIBRARIES}")
-    return()
+      _add_blas_target()
+      return()
+    endif()
   endif()
 endif()
 

Modules/FindEXPAT.cmake

@@ -49,8 +49,9 @@ cmake_policy(PUSH)
 cmake_policy(SET CMP0159 NEW) # file(STRINGS) with REGEX updates CMAKE_MATCH_<n>
 
 find_package(PkgConfig QUIET)
-
+if(PKG_CONFIG_FOUND)
-pkg_check_modules(PC_EXPAT QUIET expat)
+  pkg_check_modules(PC_EXPAT QUIET expat)
+endif()
 
 # Look for the header file.
 find_path(EXPAT_INCLUDE_DIR NAMES expat.h HINTS ${PC_EXPAT_INCLUDE_DIRS})

Modules/FindFontconfig.cmake

@@ -40,7 +40,9 @@ cmake_policy(SET CMP0159 NEW) # file(STRINGS) with REGEX updates CMAKE_MATCH_<n>
 # use pkg-config to get the directories and then use these values
 # in the FIND_PATH() and FIND_LIBRARY() calls
 find_package(PkgConfig QUIET)
-pkg_check_modules(PKG_FONTCONFIG QUIET fontconfig)
+if(PKG_CONFIG_FOUND)
+  pkg_check_modules(PKG_FONTCONFIG QUIET fontconfig)
+endif()
 set(Fontconfig_COMPILE_OPTIONS ${PKG_FONTCONFIG_CFLAGS_OTHER})
 set(Fontconfig_VERSION ${PKG_FONTCONFIG_VERSION})
 

Modules/FindGSL.cmake

@@ -81,10 +81,11 @@ endif()
 # This will return ``GSL_INCLUDEDIR`` and ``GSL_LIBDIR`` used below.
 if( GSL_USE_PKGCONFIG )
   find_package(PkgConfig QUIET)
-  pkg_check_modules( GSL QUIET gsl )
+  if(PKG_CONFIG_FOUND)
-
+    pkg_check_modules( GSL QUIET gsl )
-  if( EXISTS "${GSL_INCLUDEDIR}" )
+    if( EXISTS "${GSL_INCLUDEDIR}" )
-    get_filename_component( GSL_ROOT_DIR "${GSL_INCLUDEDIR}" DIRECTORY CACHE)
+      get_filename_component( GSL_ROOT_DIR "${GSL_INCLUDEDIR}" DIRECTORY CACHE)
+    endif()
   endif()
 endif()
 

Modules/FindGnuTLS.cmake

@@ -43,7 +43,9 @@ if (NOT WIN32)
   # in the find_path() and find_library() calls
   # also fills in GNUTLS_DEFINITIONS, although that isn't normally useful
   find_package(PkgConfig QUIET)
-  PKG_CHECK_MODULES(PC_GNUTLS QUIET gnutls)
+  if(PKG_CONFIG_FOUND)
+    PKG_CHECK_MODULES(PC_GNUTLS QUIET gnutls)
+  endif()
   set(GNUTLS_DEFINITIONS ${PC_GNUTLS_CFLAGS_OTHER})
   set(GNUTLS_VERSION ${PC_GNUTLS_VERSION})
   # keep for backward compatibility

Modules/FindImageMagick.cmake

@@ -115,7 +115,9 @@ find_package(PkgConfig QUIET)
 function(FIND_IMAGEMAGICK_API component header)
   set(ImageMagick_${component}_FOUND FALSE PARENT_SCOPE)
 
-  pkg_check_modules(PC_${component} QUIET ${component})
+  if(PKG_CONFIG_FOUND)
+    pkg_check_modules(PC_${component} QUIET ${component})
+  endif()
 
   find_path(ImageMagick_${component}_INCLUDE_DIR
     NAMES ${header}

Modules/FindLAPACK.cmake

@@ -289,15 +289,17 @@ if(BLA_PREFER_PKGCONFIG)
     set(BLA_PKGCONFIG_LAPACK "lapack")
   endif()
   find_package(PkgConfig QUIET)
-  pkg_check_modules(PKGC_LAPACK QUIET ${BLA_PKGCONFIG_LAPACK})
+  if(PKG_CONFIG_FOUND)
-  if(PKGC_LAPACK_FOUND)
+    pkg_check_modules(PKGC_LAPACK QUIET ${BLA_PKGCONFIG_LAPACK})
-    set(LAPACK_FOUND TRUE)
+    if(PKGC_LAPACK_FOUND)
-    set(LAPACK_LIBRARIES "${PKGC_LAPACK_LINK_LIBRARIES}")
+      set(LAPACK_FOUND TRUE)
-    if (BLAS_LIBRARIES)
+      set(LAPACK_LIBRARIES "${PKGC_LAPACK_LINK_LIBRARIES}")
-      list(APPEND LAPACK_LIBRARIES "${BLAS_LIBRARIES}")
+      if (BLAS_LIBRARIES)
+        list(APPEND LAPACK_LIBRARIES "${BLAS_LIBRARIES}")
+      endif()
+      _add_lapack_target()
+      return()
     endif()
-    _add_lapack_target()
-    return()
   endif()
 endif()
 

Modules/FindLibXml2.cmake

@@ -58,7 +58,9 @@ cmake_policy(SET CMP0159 NEW) # file(STRINGS) with REGEX updates CMAKE_MATCH_<n>
 # use pkg-config to get the directories and then use these values
 # in the find_path() and find_library() calls
 find_package(PkgConfig QUIET)
-PKG_CHECK_MODULES(PC_LIBXML QUIET libxml-2.0)
+if(PKG_CONFIG_FOUND)
+  PKG_CHECK_MODULES(PC_LIBXML QUIET libxml-2.0)
+endif()
 
 find_path(LIBXML2_INCLUDE_DIR NAMES libxml/xpath.h
    HINTS

Modules/FindLibXslt.cmake

@@ -51,7 +51,9 @@ cmake_policy(SET CMP0159 NEW) # file(STRINGS) with REGEX updates CMAKE_MATCH_<n>
 # use pkg-config to get the directories and then use these values
 # in the find_path() and find_library() calls
 find_package(PkgConfig QUIET)
-PKG_CHECK_MODULES(PC_LIBXSLT QUIET libxslt)
+if(PKG_CONFIG_FOUND)
+  PKG_CHECK_MODULES(PC_LIBXSLT QUIET libxslt)
+endif()
 set(LIBXSLT_DEFINITIONS ${PC_LIBXSLT_CFLAGS_OTHER})
 
 find_path(LIBXSLT_INCLUDE_DIR NAMES libxslt/xslt.h
@@ -75,7 +77,9 @@ find_library(LIBXSLT_LIBRARY NAMES xslt libxslt
 
 set(LIBXSLT_LIBRARIES ${LIBXSLT_LIBRARY})
 
-PKG_CHECK_MODULES(PC_LIBXSLT_EXSLT QUIET libexslt)
+if(PKG_CONFIG_FOUND)
+  PKG_CHECK_MODULES(PC_LIBXSLT_EXSLT QUIET libexslt)
+endif()
 set(LIBXSLT_EXSLT_DEFINITIONS ${PC_LIBXSLT_EXSLT_CFLAGS_OTHER})
 
 find_path(LIBXSLT_EXSLT_INCLUDE_DIR NAMES libexslt/exslt.h

Modules/FindLibinput.cmake

@@ -38,7 +38,9 @@ This will define the following variables in your project:
 # Use pkg-config to get the directories and then use these values
 # in the FIND_PATH() and FIND_LIBRARY() calls
 find_package(PkgConfig QUIET)
-pkg_check_modules(PKG_Libinput QUIET libinput)
+if(PKG_CONFIG_FOUND)
+  pkg_check_modules(PKG_Libinput QUIET libinput)
+endif()
 
 set(Libinput_COMPILE_OPTIONS ${PKG_Libinput_CFLAGS_OTHER})
 set(Libinput_VERSION ${PKG_Libinput_VERSION})

Modules/FindOpenSSL.cmake

@@ -207,7 +207,9 @@ endfunction()
 
 if (UNIX)
   find_package(PkgConfig QUIET)
-  pkg_check_modules(_OPENSSL QUIET openssl)
+  if(PKG_CONFIG_FOUND)
+    pkg_check_modules(_OPENSSL QUIET openssl)
+  endif()
 endif ()
 
 # Support preference of static libs by adjusting CMAKE_FIND_LIBRARY_SUFFIXES