[binutils-gdb] gdb/testsuite: fix skip-tree.exp test for PowerPC

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=8b0cba92b2f897a07c38623cba2eb4289cda1eda

commit 8b0cba92b2f897a07c38623cba2eb4289cda1eda
Author: Andrew Burgess <[email protected]>
Date:   Thu Apr 16 17:55:27 2026 +0200

    gdb/testsuite: fix skip-tree.exp test for PowerPC
    
    The gdb.base/skip-tree.exp test was added in commit:
    
      commit 5ed98c177f9a2381fe5c6ab873d05f1e5dcb8f7f
      Date:   Wed Feb 4 20:31:31 2026 +0000
    
          gdb: introduce '**' for skip globs
    
    This test currently fails on PowerPC due to architectural differences
    in function return handling.
    
    On PowerPC64 ELFv2, calls to external functions are followed by a
    `nop` instruction that serves as a placeholder for TOC pointer
    restoration. Since this `nop` typically has no DWARF line entry,
    `finish` reports the call line instead of the next line.
    
    This issue was reported here:
    
      https://inbox.sourceware.org/gdb-patches/[email protected]
    
    The fix proposed there was to add a PowerPC specific check so that the
    test would send a `next` command after using `finish` to advance to
    the expected source line.
    
    This commit actually takes a more general approach.  After calling
    `finish` we check which line we ended up on.  If it was the caller
    line then we send GDB a `next` to move to the expected line.  If we
    arrive directly at the next line, then no `next` is needed.
    
    I've tested this change on x86-64, where no `next` is needed, and
    PowerPC, where `next` is now used as required to get the test
    passing.
    
    To simplify the pattern matching in the exp file, I tweaked the source
    file slightly.  But adding a call to a dummy 'func5' it's now easy to
    pattern match as we step through 'func1', 'func2', etc.
    
    Co-Authored-By: Abhay Kandpal <[email protected]>

Diff:
---
 gdb/testsuite/gdb.base/skip-tree.c   | 11 ++++++++++-
 gdb/testsuite/gdb.base/skip-tree.exp | 32 +++++++++++++++++++++-----------
 2 files changed, 31 insertions(+), 12 deletions(-)

diff --git a/gdb/testsuite/gdb.base/skip-tree.c b/gdb/testsuite/gdb.base/skip-tree.c
index 4a254b860b1..3bedc397a85 100644
--- a/gdb/testsuite/gdb.base/skip-tree.c
+++ b/gdb/testsuite/gdb.base/skip-tree.c
@@ -22,17 +22,26 @@ extern void func4 (void);
 
 static volatile int global_var;
 
+void
+func5 (void)
+{
+  /* Nothing.  */
+}
+
 int
 main (void)
 {
+  /* Some filler before the real work starts.  */
   ++global_var;
 
   func1 ();	/* In aa/bb/file.c */
   func2 ();	/* In cc/bb/file.c */
   func3 ();	/* In dd/ee/file.c */
   func4 ();	/* In dd/ee/ff/file.c */
+  func5 ();	/* Makes exp file simpler.  */
 
-  ++global_var;	/* End marker.  */
+  /* Some filler before the function ends.  */
+  ++global_var;
 
   return 0;
 }
diff --git a/gdb/testsuite/gdb.base/skip-tree.exp b/gdb/testsuite/gdb.base/skip-tree.exp
index dc93c4cef84..b1d42ffa87e 100644
--- a/gdb/testsuite/gdb.base/skip-tree.exp
+++ b/gdb/testsuite/gdb.base/skip-tree.exp
@@ -48,7 +48,7 @@ set lineno_f1 [gdb_get_line_number "func1 ();" $srcfile]
 set lineno_f2 [gdb_get_line_number "func2 ();" $srcfile]
 set lineno_f3 [gdb_get_line_number "func3 ();" $srcfile]
 set lineno_f4 [gdb_get_line_number "func4 ();" $srcfile]
-set lineno_end [gdb_get_line_number "End marker" $srcfile]
+set lineno_f5 [gdb_get_line_number "func5 ();" $srcfile]
 
 # Compile all the source files into DESTFILE.  If RELATIVE_FILENAMES
 # is true then the compilation is done using relative filenames to the
@@ -139,19 +139,29 @@ proc run_test { file_glob skip_func1 skip_func2 skip_func3 skip_func4 \
 		     "$::decimal\\s+\\+\\+global_var_$i;"] \
 		"step into func$i"
 
-	    # Now finish the function, returning to the caller.
-	    gdb_test "finish" ".*" \
-		"finish from func$i"
+	    # Now finish the function, returning to the caller.  Some
+	    # targets, after the finish, will place the inferior back
+	    # on the calling line.  We spot this and issue a 'next' to
+	    # move forward to the next function call.
+	    set saw_next_line false
+	    set saw_previous_line false
+	    gdb_test_multiple "finish" "finish from func$i" {
+		-re -wrap "\r\n$::decimal\\s+func[expr {$i + 1}] \\(\\);\[^\r\n\]*" {
+		    pass $gdb_test_name
+		}
+		-re -wrap "\r\n$::decimal\\s+func$i \\(\\);\[^\r\n\]*" {
+		    # After 'finish' this target reports the inferior
+		    # as still on the calling line.  Use 'next' to
+		    # prepare for the next test.
+		    send_gdb "next\n"
+		    exp_continue
+		}
+	    }
 	} else {
 	    # After skipping the function, on which line should we
 	    # stop, and what does the line look like.
-	    if { $j < 5 } {
-		set lineno [set "::lineno_f$j"]
-		set after_skip_re "func$j \\(\\);\[^\r\n\]+"
-	    } else {
-		set lineno $::lineno_end
-		set after_skip_re "\\+\\+global_var;\[^\r\n\]+"
-	    }
+	    set lineno [set "::lineno_f$j"]
+	    set after_skip_re "func$j \\(\\);\[^\r\n\]+"
 
 	    # Step the inferior, we expect to skip the function.
 	    gdb_test "step" \