CTestCoverageCollectGCOV: run gcov only once

Running gcov once per .gcda file is not only inefficient, it also
generates wrong data since .gcov files can get overwritten and in
general gcov works with less information.

fakegcov.cmake needs to be able to handle multiple .gcda files for the
test to be meaningful.

Modules/CTestCoverageCollectGCOV.cmake

@@ -95,7 +95,7 @@ function(ctest_coverage_collect_gcov)
   set(gcda_files)
   set(label_files)
   if (GCOV_GLOB)
-      file(GLOB_RECURSE gfiles RELATIVE ${binary_dir} "${binary_dir}/*.gcda")
+      file(GLOB_RECURSE gfiles "${binary_dir}/*.gcda")
       list(LENGTH gfiles len)
       # if we have gcda files then also grab the labels file for that target
       if(${len} GREATER 0)
@@ -109,7 +109,7 @@ function(ctest_coverage_collect_gcov)
     file(STRINGS "${binary_dir}/CMakeFiles/TargetDirectories.txt" target_dirs
          ENCODING UTF-8)
     foreach(target_dir ${target_dirs})
-      file(GLOB_RECURSE gfiles RELATIVE ${binary_dir} "${target_dir}/*.gcda")
+      file(GLOB_RECURSE gfiles "${target_dir}/*.gcda")
       list(LENGTH gfiles len)
       # if we have gcda files then also grab the labels file for that target
       if(${len} GREATER 0)
@@ -132,27 +132,21 @@ function(ctest_coverage_collect_gcov)
   # setup the dir for the coverage files
   set(coverage_dir "${binary_dir}/Testing/CoverageInfo")
   file(MAKE_DIRECTORY  "${coverage_dir}")
-  # call gcov on each .gcda file
-  foreach (gcda_file ${gcda_files})
-    # get the directory of the gcda file
-    get_filename_component(gcda_file ${binary_dir}/${gcda_file} ABSOLUTE)
-    get_filename_component(gcov_dir ${gcda_file} DIRECTORY)
-    # run gcov, this will produce the .gcov file in the current
-    # working directory
-    if(NOT DEFINED GCOV_GCOV_OPTIONS)
-      set(GCOV_GCOV_OPTIONS -b)
-    endif()
-    execute_process(COMMAND
-      ${gcov_command} ${GCOV_GCOV_OPTIONS} -o ${gcov_dir} ${gcda_file}
-      OUTPUT_VARIABLE out
-      RESULT_VARIABLE res
-      WORKING_DIRECTORY ${coverage_dir})
-
-    if (GCOV_DELETE)
-      file(REMOVE ${gcda_file})
-    endif()
+  # run gcov, this will produce the .gcov files in the current
+  # working directory
+  if(NOT DEFINED GCOV_GCOV_OPTIONS)
+    set(GCOV_GCOV_OPTIONS -b)
+  endif()
+  execute_process(COMMAND
+    ${gcov_command} ${GCOV_GCOV_OPTIONS} ${gcda_files}
+    OUTPUT_VARIABLE out
+    RESULT_VARIABLE res
+    WORKING_DIRECTORY ${coverage_dir})
+
+  if (GCOV_DELETE)
+    file(REMOVE ${gcda_files})
+  endif()
 
-  endforeach()
   if(NOT "${res}" EQUAL 0)
     if (NOT GCOV_QUIET)
       message(STATUS "Error running gcov: ${res} ${out}")

Tests/CTestCoverageCollectGCOV/fakegcov.cmake

+function(create_gcov_file gcda_full_path)
+  get_filename_component(gcda_name ${gcda_full_path} NAME)
+  string(REPLACE ".gcda" ".gcov" gcov_name "${gcda_name}")
+
+  file(STRINGS "${gcda_full_path}" source_file LIMIT_COUNT 1 ENCODING UTF-8)
+
+  file(WRITE "${CMAKE_SOURCE_DIR}/${gcov_name}"
+    "        -:    0:Source:${source_file}"
+  )
+endfunction()
+
 foreach(I RANGE 0 ${CMAKE_ARGC})
   if("${CMAKE_ARGV${I}}" MATCHES ".*\\.gcda")
     set(gcda_file "${CMAKE_ARGV${I}}")
+    create_gcov_file(${gcda_file})
   endif()
 endforeach()
-
-get_filename_component(gcda_name ${gcda_file} NAME)
-string(REPLACE ".gcda" ".gcov" gcov_name "${gcda_name}")
-
-file(STRINGS "${gcda_file}" source_file LIMIT_COUNT 1 ENCODING UTF-8)
-
-file(WRITE "${CMAKE_SOURCE_DIR}/${gcov_name}"
-  "        -:    0:Source:${source_file}"
-)