MDEV-20787: Script dgcov.pl does not workbb-10.2-anel-MDEV-20787

Let's change CMakeList with `--coverage` flag as an alias for
`-fprofile-arcs -ftest-coverage -lgcov` in addition.
When the server is compiled with `-DENABLE_GCOV=ON`, from object files are generated
`.gcno` and `.gcda` files.
`./mtr --gcov is_check_constraint` is invoking the script calls
`./dgcov.pl --purge`, `./mtr is_check_constraint`,
`./dgcov.pl --generate>/var/last_changes.dgcov`.
The `purge` flag is clearing `.gcda` files (and others extensions),
while running the test new `.gcda` files are obtained.
With `generate` flag, `gcov -i` (`intermediate format`) is called
on obtained `<object-files-name>.gcda` files (`dbug.c.gcda` e.g.).
The patch is tested on `gcov 6.3` and `gcov 7.4` versions
and can be seen that resulting `.gcov` file for `6.3` creates
`<full path>.gcov` (`dbug.c.gcda.gcov` e.g.) file,
where `gcov 7.4` is still creating `object-file-names.gcov`(`dbug.c.gcov`) files
as `gcov` in general is doing.

2 files changed, 15 insertions, 3 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0dcc2a75587..af025a0312f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -249,7 +249,7 @@ SET(CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS_DEBUG} -DENABLED_DEBUG_SYNC")
  
 OPTION(ENABLE_GCOV "Enable gcov (debug, Linux builds only)" OFF)
 IF (ENABLE_GCOV)
-  MY_CHECK_AND_SET_COMPILER_FLAG("-fprofile-arcs -ftest-coverage -lgcov" DEBUG)
+  MY_CHECK_AND_SET_COMPILER_FLAG("--coverage" DEBUG)
 ENDIF()
 
 MY_CHECK_AND_SET_COMPILER_FLAG(-ggdb3 DEBUG)
diff --git a/mysql-test/dgcov.pl b/mysql-test/dgcov.pl
index fbc5540e697..47ffaca04ef 100755
--- a/mysql-test/dgcov.pl
+++ b/mysql-test/dgcov.pl
@@ -68,8 +68,11 @@ if ($opt_purge)
   system($cmd)==0 or die "system($cmd): $? $!";
   exit 0;
 }
-
+my $gcov_vers= `gcov -v`;
+$gcov_vers=~ s/\D//g;
+$gcov_vers= substr($gcov_vers, 0, 1);
 find(\&gcov_one_file, $root);
+undef $gcov_vers;
 find(\&write_coverage, $root) if $opt_generate;
 exit 0 if $opt_only_gcov;
 
@@ -162,7 +165,16 @@ sub gcov_one_file {
   }
 
   # now, read the generated file
-  open FH, '<', "$_.gcov" or die "open(<$_.gcov): $!";
+  if($gcov_vers<7)
+  {
+    open FH, '<', "$_.gcov" or die "open(<$_.gcov): $!";
+  }
+  else
+  {
+    my $f=substr $_, 0, -5;
+    open FH, '<', "$f.gcov" or die "open(<$f.gcov): $!";
+    undef $f;
+  }
   my $fname;
   while (<FH>) {
     chomp;