gdb/gdb-bz533176-fortran-omp-step.patch

From FEDORA_PATCHES Mon Sep 17 00:00:00 2001
From: Fedora GDB patches <invalid@email.com>
Date: Fri, 27 Oct 2017 21:07:50 +0200
Subject: gdb-bz533176-fortran-omp-step.patch

;; Fix stepping with OMP parallel Fortran sections (BZ 533176).
;;=push+jan: It requires some better DWARF annotations.

https://bugzilla.redhat.com/show_bug.cgi?id=533176#c4

I find it a bug in DWARF and gdb behaves correctly according to it.  From the
current DWARF's point of view the is a function call which you skip by "next".

If you hide any /usr/lib/debug such as using:
gdb -nx -ex 'set debug-file-directory /qwe' -ex 'file ./tpcommon_gfortran44'
and use "step" command instead of "next" there it will work.
(You need to hide debuginfo from libgomp as you would step into libgomp sources
to maintain the threads for execution.)

There should be some DWARF extension for it, currently tried to detect
substring ".omp_fn." as this function is called "MAIN__.omp_fn.0" and do not
consider such sub-function as a skippable by "next".

Another problem is that with "set scheduler-locking" being "off" (default
upstream) or "step" (default in F/RHEL) the simultaneous execution of the
threads is inconvenient.  Setting it to "on" will lockup the debugging as the
threads need to get synchronized at some point.  This is a more general
debugging problem of GOMP outside of the scope of this Bug.

diff --git a/gdb/infrun.c b/gdb/infrun.c
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -6460,6 +6460,16 @@ process_event_stop_test (struct execution_control_state *ecs)
 
       if (ecs->event_thread->control.step_over_calls == STEP_OVER_ALL)
 	{
+	  struct symbol *stop_fn = find_pc_function (stop_pc);
+	  struct minimal_symbol *stopf = lookup_minimal_symbol_by_pc (stop_pc).minsym;
+
+	  if ((stop_fn == NULL
+	       || strstr (SYMBOL_LINKAGE_NAME (stop_fn), ".omp_fn.") == NULL)
+	      /* gcc-4.7.2-9.fc19.x86_64 uses a new format.  */
+	      && (stopf == NULL
+		  || strstr (MSYMBOL_LINKAGE_NAME (stopf), "._omp_fn.") == NULL))
+{	/* ".omp_fn." */
+
 	  /* We're doing a "next".
 
 	     Normal (forward) execution: set a breakpoint at the
@@ -6493,6 +6503,7 @@ process_event_stop_test (struct execution_control_state *ecs)
 
 	  keep_going (ecs);
 	  return;
+}	/* ".omp_fn." */
 	}
 
       /* If we are in a function call trampoline (a stub between the
diff --git a/gdb/testsuite/gdb.fortran/omp-step.exp b/gdb/testsuite/gdb.fortran/omp-step.exp
new file mode 100644
--- /dev/null
+++ b/gdb/testsuite/gdb.fortran/omp-step.exp
@@ -0,0 +1,31 @@
+# Copyright 2009 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+set testfile "omp-step"
+set srcfile ${testfile}.f90
+if { [prepare_for_testing $testfile.exp $testfile $srcfile {debug f90 additional_flags=-fopenmp}] } {
+    return -1
+}
+
+if ![runto [gdb_get_line_number "start-here"]] {
+    perror "Couldn't run to start-here"
+    return 0
+}
+
+gdb_test "next" {!\$omp parallel} "step closer"
+gdb_test "next" {a\(omp_get_thread_num\(\) \+ 1\) = 1} "step into omp"
+
+gdb_breakpoint [gdb_get_line_number "success"]
+gdb_continue_to_breakpoint "success" ".*success.*"
diff --git a/gdb/testsuite/gdb.fortran/omp-step.f90 b/gdb/testsuite/gdb.fortran/omp-step.f90
new file mode 100644
--- /dev/null
+++ b/gdb/testsuite/gdb.fortran/omp-step.f90
@@ -0,0 +1,32 @@
+! Copyright 2009 Free Software Foundation, Inc.
+
+! This program is free software; you can redistribute it and/or modify
+! it under the terms of the GNU General Public License as published by
+! the Free Software Foundation; either version 3 of the License, or
+! (at your option) any later version.
+!
+! This program is distributed in the hope that it will be useful,
+! but WITHOUT ANY WARRANTY; without even the implied warranty of
+! MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+! GNU General Public License for more details.
+!
+! You should have received a copy of the GNU General Public License
+! along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+      use omp_lib
+      integer nthreads, i, a(1000)
+      nthreads = omp_get_num_threads()
+      if (nthreads .gt. 1000) call abort
+
+      do i = 1, nthreads
+          a(i) = 0
+      end do
+      print *, "start-here"
+!$omp parallel
+      a(omp_get_thread_num() + 1) = 1
+!$omp end parallel
+      do i = 1, nthreads
+          if (a(i) .ne. 1) call abort
+      end do
+      print *, "success"
+      end