[binutils-gdb] gdb/testsuite: Fix race condition in gdb.base/skip.exp

[Andrew Burgess]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=3be966f69d6967d2857baa3efb0bc043081e0a00

commit 3be966f69d6967d2857baa3efb0bc043081e0a00
Author: Andrew Burgess <andrew.burgess@embecosm.com>
Date:   Thu Jan 9 22:38:22 2020 +0000

    gdb/testsuite: Fix race condition in gdb.base/skip.exp
    
    In this commit:
    
      commit 5024637fac653914d471808288dc3221bc7ec089
      Date:   Sun Dec 15 11:05:47 2019 +0100
    
          Fix skip.exp test failure observed with gcc-9.2.0
    
    A race condition was introduced into the gdb.base/skip.exp test when
    this line:
    
        gdb_test "step" "foo \\(\\) at.*" "step 3"
    
    Was changed to this:
    
        gdb_test "step" "foo \\(\\) at.*" "step 3" "main \\(\\) at .*" "step"
    
    Before the above change we expected GDB to behave like this:
    
      (gdb) step
      foo () at /path/to/gdb/testsuite/gdb.base/skip.c:42
      42        return 0;
      (gdb)
    
    However, when the test is compiled with GCC 9.2.0 we get a different
    behaviour, and so we need a second 'step', like this:
    
      (gdb) step
      main () at /path/to/gdb.base/skip.c:32
      32        x = baz ((bar (), foo ()));
      (gdb) step
      foo () at /path/to/gdb/testsuite/gdb.base/skip.c:42
      42        return 0;
      (gdb)
    
    Now the change to the test matches against 'main () at .*', however if
    GDB or expect is being slow then we might only get to see output like
    this:
    
      (gdb) step
      main () at /path/to/g
    
    This will happily match the question pattern, so we send 'step' to GDB
    again.  Now GDB continues to produce output which expect accepts, we
    now see this:
    
      b.base/skip.c:32
      32        x = baz ((bar (), foo ()));
      (gdb)
    
    This has carried on from where the previous block of output left off.
    This doesn't match the final pattern 'foo \\(\\) at.*', but it does
    match the prompt pattern that gdb_test_multiple adds, and so we report
    the test as failing.
    
    The solution is to simply ensure that the question consumes everything
    up to, and including the prompt.  This ensures that the prompt can't
    then match the failure case.  The new test line becomes:
    
        gdb_test "step" "foo \\(\\) at.*" "step 3" \
           "main \\(\\) at .*\r\n$gdb_prompt " "step"
    
    gdb/testsuite/ChangeLog:
    
    	* gdb.base/skip.exp: Fix race condition in test.
    
    Change-Id: I9f0b0b52ef1b4f980bfaa8fe405ff06d520f3482

Diff:
---
 gdb/testsuite/ChangeLog         | 4 ++++
 gdb/testsuite/gdb.base/skip.exp | 9 ++++++---
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 3f24364..cecd384 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2020-01-09  Andrew Burgess  <andrew.burgess@embecosm.com>
+
+	* gdb.base/skip.exp: Fix race condition in test.
+
 2020-01-06  Andrew Burgess  <andrew.burgess@embecosm.com>
 
 	* gdb.base/backtrace.c: New file.
diff --git a/gdb/testsuite/gdb.base/skip.exp b/gdb/testsuite/gdb.base/skip.exp
index d7dd3ce..513c9fc 100644
--- a/gdb/testsuite/gdb.base/skip.exp
+++ b/gdb/testsuite/gdb.base/skip.exp
@@ -144,7 +144,8 @@ with_test_prefix "step after disabling 3" {
     gdb_test "step" ".*" "step 2"; # Return from bar()
     # With gcc 9.2.0 we jump once back to main before entering foo here.
     # If that happens try to step a second time.
-    gdb_test "step" "foo \\(\\) at.*" "step 3" "main \\(\\) at .*" "step"
+    gdb_test "step" "foo \\(\\) at.*" "step 3" \
+	"main \\(\\) at .*\r\n$gdb_prompt " "step"
     gdb_test "step" ".*" "step 4"; # Return from foo()
     gdb_test "step" "main \\(\\) at.*" "step 5"
 }
@@ -265,7 +266,8 @@ with_test_prefix "step using -fu for baz" {
     gdb_test "step" ".*" "step 2"; # Return from bar()
     # With gcc 9.2.0 we jump once back to main before entering foo here.
     # If that happens try to step a second time.
-    gdb_test "step" "foo \\(\\) at.*" "step 3" "main \\(\\) at.*" "step"
+    gdb_test "step" "foo \\(\\) at.*" "step 3" \
+	"main \\(\\) at .*\r\n$gdb_prompt " "step"
     gdb_test "step" ".*" "step 4"; # Return from foo()
     gdb_test "step" "main \\(\\) at.*" "step 5"
 }
@@ -282,7 +284,8 @@ with_test_prefix "step using -rfu for baz" {
     gdb_test "step" ".*" "step 2"; # Return from bar()
     # With gcc 9.2.0 we jump once back to main before entering foo here.
     # If that happens try to step a second time.
-    gdb_test "step" "foo \\(\\) at.*" "step 3" "main \\(\\) at.*" "step"
+    gdb_test "step" "foo \\(\\) at.*" "step 3" \
+	"main \\(\\) at .*\r\n$gdb_prompt " "step"
     gdb_test "step" ".*" "step 4"; # Return from foo()
     gdb_test "step" "main \\(\\) at.*" "step 5"
 }