configure: query pkg-config for flags & libraries for gtest

See #3696

NEWS.md

@@ -4,6 +4,9 @@
 
 * fixed compilation of `src/common/sorting.h` with certain compilers due to
   the deprecation & removal of `std::result_of<>` in C++20. Fixes #3695.
+* fixed compilation with the `gtest` library when `gtest` requires additional
+  libraries by querying `pkg-config` for the correct flags & libraries to
+  build with. See #3696.
 
 
 # Version 84.0 "Sleeper" 2024-04-28

Rakefile

@@ -171,7 +171,7 @@ def setup_globals
   cxxflags                += " -Wmisleading-indentation -Wduplicated-cond"                               if check_compiler_version("gcc", "6.0.0")
   cxxflags                += " -Wshadow-compatible-local -Wduplicated-branches"                          if check_compiler_version("gcc", "7.0.0")
   cxxflags                += " -Wno-deprecated-copy -Wno-stringop-overflow"                              if check_compiler_version("gcc", "9.0.0")
-  cxxflags                += " #{c(:QT_CFLAGS)} #{c(:BOOST_CPPFLAGS)} #{c(:USER_CXXFLAGS)}"
+  cxxflags                += " #{c(:QT_CFLAGS)} #{c(:BOOST_CPPFLAGS)} #{c(:USER_CXXFLAGS)} #{c(:GTEST_CFLAGS)}"
 
   ldflags                  = ""
   ldflags                 += determine_stack_protector_flags

ac/gtest.m4

@@ -1,13 +1,20 @@
 AC_DEFUN([AX_GTEST],[
-  GTEST_TYPE=system
+  GTEST_CFLAGS=
+  GTEST_LIBS=
+  GTEST_TYPE=no
 
   CPPFLAGS_SAVED="$CPPFLAGS"
   AC_LANG_PUSH(C++)
 
-  AC_CHECK_LIB([gtest_main],[main],[true],[GTEST_TYPE=no],[-lpthread])
-  AC_CHECK_HEADERS([gtest/gtest.h],[true],[GTEST_TYPE=no])
+  PKG_CHECK_EXISTS([gtest],[gtest_found=yes],[gtest_found=no])
 
-  if test $GTEST_TYPE = no && test -d lib/gtest/include && test -d lib/gtest/src ; then
+  if test x"$gtest_found" = xyes; then
+    PKG_CHECK_MODULES([gtest],[gtest],[gtest_found=yes])
+    GTEST_CFLAGS="`$PKG_CONFIG --cflags gtest`"
+    GTEST_LIBS="`$PKG_CONFIG --libs gtest`"
+    GTEST_TYPE=system
+
+  elif test -d lib/gtest/include && test -d lib/gtest/src ; then
     AC_MSG_CHECKING(for internal gtest)
     AC_CACHE_VAL(ax_cv_gtest_internal,[
       CPPFLAGS="$CPPFLAGS_SAVED -Ilib/gtest/include"
@@ -23,6 +30,8 @@ AC_DEFUN([AX_GTEST],[
   AC_LANG_POP
   CPPFLAGS="$CPPFLAGS_SAVED"
 
+  AC_SUBST(GTEST_CFLAGS)
+  AC_SUBST(GTEST_LIBS)
   AC_SUBST(GTEST_TYPE)
 ])
 

build-config.in

@@ -98,6 +98,8 @@ EXTRA_CFLAGS = @EXTRA_CFLAGS@
 EXTRA_LDFLAGS = @EXTRA_LDFLAGS@
 FMT_INTERNAL = @FMT_INTERNAL@
 GOOGLE_BENCHMARK = @GOOGLE_BENCHMARK@
+GTEST_CFLAGS = @GTEST_CFLAGS@
+GTEST_LIBS = @GTEST_LIBS@
 GTEST_TYPE = @GTEST_TYPE@
 LDFLAGS_RPATHS = @LDFLAGS_RPATHS@
 FLAC_CFLAGS = @FLAC_CFLAGS@

rake.d/gtest.rb

@@ -24,7 +24,6 @@ $build_system_modules[:gtest] = {
   :setup => lambda do
     if $gtest_internal
       $flags[:cxxflags] += " -Ilib/gtest -Ilib/gtest/include"
-      $flags[:ldflags]  += " -Llib/gtest/src"
     end
   end,
 

rake.d/target.rb

@@ -158,6 +158,7 @@ class Target
       case entry
       when nil               then nil
       when :flac             then c(:FLAC_LIBS)
+      when :gtest            then $gtest_internal ? [ '-Llib/gtest/src', '-lgtest' ] : c(:GTEST_LIBS)
       when :iconv            then c(:ICONV_LIBS)
       when :intl             then c(:LIBINTL_LIBS)
       when :cmark            then c(:CMARK_LIBS)