[PATCH v6 07/10] gdb: Skip trampoline functions for the return command.

[Abdul Basit Ijaz <abdul.b.ijaz@intel.com>]

From: "Ijaz, Abdul B" <abdul.b.ijaz@intel.com>

This change skips trampoline functions for the return command
when the option 'skip-trampoline-functions' is set to 'on'.  Before this
change, GDB processes trampoline functions indicated by the compiler with
DIE "DW_AT_trampoline" for the return command and stops at the trampoline
functions.  For better user experience, all such frames can
be skipped and hidden from the user.

In this example the IFX compiler emits "DW_AT_trampoline" tag for the 'first'
and 'second' trampoline functions like following:

function second (x, y) result(z)
  integer, intent(in) :: x, y
  integer :: z
  z = x * y ! breakpt-return
end function second

function first (num1, num2) result(total)
  integer, intent(in) :: num1, num2
  integer  :: total
  total = second (num1 + 4, num2 * 3) ! first-breakpt
  total = total + 30
end function first

Related Dwarf:

0x0000013f:   DW_TAG_subprogram
                DW_AT_low_pc    (0x0000000000404350)
                DW_AT_high_pc   (0x000000000040435f)
                DW_AT_frame_base        (DW_OP_reg6 RBP)
                DW_AT_linkage_name      ("second_.t74p.t75p")
                DW_AT_name      ("second_.t74p.t75p")
                DW_AT_trampoline        ("second_")

0x0000015a:   DW_TAG_subprogram
                DW_AT_low_pc    (0x00000000004044a0)
                DW_AT_high_pc   (0x00000000004044af)
                DW_AT_frame_base        (DW_OP_reg6 RBP)
                DW_AT_linkage_name      ("first_.t104p.t105p")
                DW_AT_name      ("first_.t104p.t105p")
                DW_AT_trampoline        ("first_")

Before this change, the return command output looks like:

'''
(gdb) return
Make second return now? (y or n) y
\#0  0x0000000000405209 in second_.t74p.t75p () at test.f90:12
12      end function first
'''

After this change:

'''
(gdb) return
Make second return now? (y or n) y
\#0  0x00000000004051e3 in first (num1=16, num2=3) at test.f90:10
10        total = second (num1 + 4, num2 * 3) ! first-breakpt
'''

The test gdb.fortran/func-trampoline.exp is updated for testing this change.

2024-03-28 Ijaz, Abdul B <abdul.b.ijaz@intel.com>
---
 gdb/doc/gdb.texinfo                           |  6 +++---
 gdb/stack.c                                   | 11 +++++++++++
 gdb/testsuite/gdb.fortran/func-trampoline.exp | 10 +++++++++-
 3 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 222faba5da3..a6f74373dfe 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -6475,9 +6475,9 @@ DWARF trampolines marked via DW_AT_trampoline are supported by this.
 When issuing a @code{backtrace}, if @code{skip-trampoline-functions} is set,
 @value{GDBN} will skip trampoline frames while printing the stack.
 
-When issuing a @code{finish}, @code{reverse-finish} or @code{up}, if
-@code{skip-trampoline-functions} is set, @value{GDBN} will skip trampoline
-frames while returning from the target function.
+When issuing a @code{finish}, @code{reverse-finish}, @code{up} or
+@code{return}, if @code{skip-trampoline-functions} is set, @value{GDBN} will
+skip trampoline frames while returning from the target function.
 
 Currently, only DWARF trampolines marked via DW_AT_trampoline are supported by
 this.
diff --git a/gdb/stack.c b/gdb/stack.c
index 2071d98ffe6..85deedce682 100644
--- a/gdb/stack.c
+++ b/gdb/stack.c
@@ -2836,6 +2836,17 @@ return_command (const char *retval_exp, int from_tty)
   if (get_frame_type (get_current_frame ()) == DUMMY_FRAME)
     frame_pop (get_current_frame ());
 
+  if (skip_trampoline_functions)
+    {
+      frame_info_ptr ret_frame = get_current_frame ();
+      for (int i = 0; (SAFE_TRAMPOLINE_CHAIN (i, ret_frame)
+		       && in_trampoline_frame (ret_frame)); ++i)
+	{
+	  frame_pop (ret_frame);
+	  ret_frame = get_current_frame ();
+	}
+    }
+
   select_frame (get_current_frame ());
   /* If interactive, print the frame that is now current.  */
   if (from_tty)
diff --git a/gdb/testsuite/gdb.fortran/func-trampoline.exp b/gdb/testsuite/gdb.fortran/func-trampoline.exp
index e7e4c8ae7b0..dd26e5ab035 100644
--- a/gdb/testsuite/gdb.fortran/func-trampoline.exp
+++ b/gdb/testsuite/gdb.fortran/func-trampoline.exp
@@ -13,7 +13,7 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/> .
 
-# Test "backtrace", "backtrace -n", "finish" and "up"  commands for
+# Test "backtrace", "backtrace -n", "finish", "up" and "return" commands for
 # functions with trampoline calls.
 
 require allow_fortran_tests
@@ -92,3 +92,11 @@ with_test_prefix "up" {
 	"#$decimal.* $middle_desc" \
 	"${fill}first = second \\(num1 \\+ 4, num2 \\* 3\\).*${fill}"]
 }
+
+with_test_prefix "return" {
+    init_test
+
+    gdb_test "return" \
+	".*first = second \\(num1 \\+ 4, num2 \\* 3\\) \\! first-breakpt" \
+	"" "Make second return now.*y or n. $" "y"
+}
-- 
2.34.1

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