[pushed 1/2] [gdb/testsuite] Make gdb.base/longjmp.exp FAIL more stable across archs

[pushed 1/2] [gdb/testsuite] Make gdb.base/longjmp.exp FAIL more stable across archs

[Tom de Vries]

When running test-case gdb.base/longjmp.exp on x86_64-linux, the master
longjmp breakpoint is set using probes and the test-case passes:
...
(gdb) PASS: gdb.base/longjmp.exp: next to longjmp (1)
next^M
0x00000000004005cc      49        if (setjmp (env) == 0) /* patt1 */^M
(gdb) PASS: gdb.base/longjmp.exp: next over longjmp(1)
next^M
56            resumes++;^M
(gdb) PASS: gdb.base/longjmp.exp: next into else block (1)
...

However, if I disable
create_longjmp_master_breakpoint_probe, we have instead:
...
(gdb) PASS: gdb.base/longjmp.exp: next to longjmp (1)
next^M
56            resumes++;^M
(gdb) FAIL: gdb.base/longjmp.exp: next over longjmp(1)
...

At first glance, the failure mode doesn't look too bad: we stop
a few insns later than the passing scenario.

For contrast, if we do the same on powerpc64le, the failure mode is:
...
(gdb) PASS: gdb.base/longjmp.exp: next to longjmp (1)
next^M
^M
Breakpoint 3, main () at longjmp.c:59^M
59        i = 1; /* miss_step_1 */^M
(gdb) FAIL: gdb.base/longjmp.exp: next over longjmp(1)
...
Here we only stop because of running into the safety net breakpoint at
miss_step_1.

So, how does this happen on x86_64?  Let's look at the code:
...
4005c7: e8 94 fe ff ff    call 400460 <_setjmp@plt>
4005cc: 85 c0             test %eax,%eax
4005ce: 75 1e             jne  4005ee <main+0x3b>
4005d0: 8b 05 8e 0a 20 00 mov  0x200a8e(%rip),%eax # 601064 <longjmps>
4005d6: 83 c0 01          add  $0x1,%eax
4005d9: 89 05 85 0a 20 00 mov  %eax,0x200a85(%rip) # 601064 <longjmps>
4005df: be 01 00 00 00    mov  $0x1,%esi
4005e4: bf 80 10 60 00    mov  $0x601080,%edi
4005e9: e8 82 fe ff ff    call 400470 <longjmp@plt>
4005ee: 8b 05 74 0a 20 00 mov  0x200a74(%rip),%eax # 601068 <resumes>
...
The next over the longjmp call at 4005e9 is supposed to stop at the longjmp
target at 4005cc, but instead we stop at 4005ee, where we have the step-resume
breakpoint inserted by the next.  In other words, we accidentally "return"
from the longjmp call to the insn immediately after it (even though
a longjmp is a noreturn function).

Try to avoid this accident and make the failure mode on x86_64 the same as on
powerpc64le, by switching the then and else branch.

Tested on x86_64-linux.
---
 gdb/testsuite/gdb.base/longjmp.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/gdb/testsuite/gdb.base/longjmp.c b/gdb/testsuite/gdb.base/longjmp.c
index 4139e49e6f1..ce6990ca99a 100644
--- a/gdb/testsuite/gdb.base/longjmp.c
+++ b/gdb/testsuite/gdb.base/longjmp.c
@@ -46,14 +46,14 @@ main ()
   volatile int i = 0;
 
   /* Pattern 1 - simple longjmp.  */
-  if (setjmp (env) == 0) /* patt1 */
+  if (setjmp (env) != 0) /* patt1 */
     {
-      longjmps++;
-      longjmp (env, 1);
+      resumes++;
     }
   else
     {
-      resumes++;
+      longjmps++;
+      longjmp (env, 1);
     }
 
   i = 1; /* miss_step_1 */

base-commit: c8ea5e409b02cf7fa848e44af74b2e8246ad03f1
-- 
2.35.3

[pushed 2/2] [gdb/testsuite] Fix test names in gdb.base/longjmp.exp

[Tom de Vries]

When running test-case gdb.base/longjmp.exp, we have:
...
PASS: gdb.base/longjmp.exp: next over setjmp (1)
  ...
PASS: gdb.base/longjmp.exp: next over setjmp (2)
...

The trailing " (1)" and " (2)" are interpreted as comments rather than parts
of the test name, and therefore this is a duplicate, which is currently not
detected by our duplicate detection mechanism (PR testsuite/29772).

Fix the duplicate by using with_test_prefix.

Tested on x86_64-linux.
---
 gdb/testsuite/gdb.base/longjmp.exp | 111 ++++++++++++++++-------------
 1 file changed, 63 insertions(+), 48 deletions(-)

diff --git a/gdb/testsuite/gdb.base/longjmp.exp b/gdb/testsuite/gdb.base/longjmp.exp
index bd2fc21a442..10e440bfca8 100644
--- a/gdb/testsuite/gdb.base/longjmp.exp
+++ b/gdb/testsuite/gdb.base/longjmp.exp
@@ -42,30 +42,35 @@ set bp_start_test_3 [gdb_get_line_number "patt3"]
 # Pattern 1 - simple longjmp.
 #
 
-delete_breakpoints
-
-gdb_test "break $bp_start_test_1" \
-    "Breakpoint.*at.* file .*$srcfile, line.*$bp_start_test_1.*" \
-    "breakpoint at pattern 1 start"
-gdb_test "continue" "patt1.*" "continue to breakpoint at pattern 1 start"
-
-# set safe-net break
-gdb_test "break $bp_miss_step_1" \
-    "Breakpoint.*at.* file .*$srcfile, line.*$bp_miss_step_1.*" \
-    "breakpoint at miss_step_1"
-
-gdb_test "next" "longjmps\\+\\+;.*" "next over setjmp (1)"
-gdb_test "next" "longjmp \\(env, 1\\);.*" "next to longjmp (1)"
-
-set msg "next over longjmp(1)"
-gdb_test_multiple "next" $msg {
-    -re ".*patt1.*$gdb_prompt $" {
-	pass $msg
-	gdb_test "next" "resumes\\+\\+.*" "next into else block (1)"
-	gdb_test "next" "miss_step_1.*" "next into safety net (1)"
+with_test_prefix "pattern 1" {
+
+    with_test_prefix setup {
+	delete_breakpoints
+
+	gdb_test "break $bp_start_test_1" \
+	    "Breakpoint.*at.* file .*$srcfile, line.*$bp_start_test_1.*" \
+	    "breakpoint at pattern start"
+	gdb_test "continue" "patt1.*" "continue to breakpoint at pattern start"
+
+	# set safe-net break
+	gdb_test "break $bp_miss_step_1" \
+	    "Breakpoint.*at.* file .*$srcfile, line.*$bp_miss_step_1.*" \
+	    "breakpoint at safety net"
     }
-    -re "miss_step_1.*$gdb_prompt $" {
-	fail $msg
+
+    gdb_test "next" "longjmps\\+\\+;.*" "next over setjmp"
+    gdb_test "next" "longjmp \\(env, 1\\);.*" "next to longjmp"
+
+    set msg "next over longjmp"
+    gdb_test_multiple "next" $msg {
+	-re ".*patt1.*$gdb_prompt $" {
+	    pass $msg
+	    gdb_test "next" "resumes\\+\\+.*" "next into else block"
+	    gdb_test "next" "miss_step_1.*" "next into safety net"
+	}
+	-re "miss_step_1.*$gdb_prompt $" {
+	    fail $msg
+	}
     }
 }
 
@@ -73,30 +78,35 @@ gdb_test_multiple "next" $msg {
 # Pattern 2 - longjmp from an inner function.
 #
 
-delete_breakpoints
+with_test_prefix "pattern 2" {
+
+    with_test_prefix setup {
+	delete_breakpoints
 
-gdb_test "break $bp_start_test_2" \
-    "Breakpoint.*at.* file .*$srcfile, line.*$bp_start_test_2.*" \
-    "breakpoint at pattern 2 start"
-gdb_test "continue" "patt2.*" "continue to breakpoint at pattern 2 start"
+	gdb_test "break $bp_start_test_2" \
+	    "Breakpoint.*at.* file .*$srcfile, line.*$bp_start_test_2.*" \
+	    "breakpoint at pattern start"
+	gdb_test "continue" "patt2.*" "continue to breakpoint at pattern start"
 
-# set safe-net break
-gdb_test "break $bp_miss_step_2" \
-    "Breakpoint.*at.* file .*$srcfile, line.*$bp_miss_step_2.*" \
-    "breakpoint at miss_step_2"
+	# set safe-net break
+	gdb_test "break $bp_miss_step_2" \
+	    "Breakpoint.*at.* file .*$srcfile, line.*$bp_miss_step_2.*" \
+	    "breakpoint at safety net"
+    }
 
-gdb_test "next" "call_longjmp.*" "next over setjmp (2)"
+    gdb_test "next" "call_longjmp.*" "next over setjmp"
 
-set msg "next over call_longjmp (2)"
-gdb_test_multiple "next" $msg {
-    -re ".*patt2.*$gdb_prompt $" {
-	pass $msg
+    set msg "next over call_longjmp"
+    gdb_test_multiple "next" $msg {
+	-re ".*patt2.*$gdb_prompt $" {
+	    pass $msg
 
-	gdb_test "next" "resumes\\+\\+.*" "next into else block (2)"
-	gdb_test "next" "miss_step_2.*" "next into safety net (2)"
-    }
-    -re "miss_step_2.*$gdb_prompt $" {
-	fail $msg
+	    gdb_test "next" "resumes\\+\\+.*" "next into else block"
+	    gdb_test "next" "miss_step_2.*" "next into safety net"
+	}
+	-re "miss_step_2.*$gdb_prompt $" {
+	    fail $msg
+	}
     }
 }
 
@@ -104,11 +114,16 @@ gdb_test_multiple "next" $msg {
 # Pattern 3 - setjmp/longjmp inside stepped-over function.
 #
 
-delete_breakpoints
+with_test_prefix "pattern 3" {
 
-gdb_test "break $bp_start_test_3" \
-    "Breakpoint.*at.* file .*$srcfile, line.*$bp_start_test_3.*" \
-    "breakpoint at pattern 3 start"
-gdb_test "continue" "patt3.*" "continue to breakpoint at pattern 3 start"
+    with_test_prefix setup {
+	delete_breakpoints
 
-gdb_test "next" "longjmp caught.*" "next over patt3"
+	gdb_test "break $bp_start_test_3" \
+	    "Breakpoint.*at.* file .*$srcfile, line.*$bp_start_test_3.*" \
+	    "breakpoint at pattern start"
+	gdb_test "continue" "patt3.*" "continue to breakpoint at pattern start"
+    }
+
+    gdb_test "next" "longjmp caught.*" "next over pattern"
+}
-- 
2.35.3