[binutils-gdb] gdb/testsuite: fix gdb.base/break-idempotent.exp on ppc

[Andrew Burgess <aburgess@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=13f72372413400410aaa94b7f0e2ff7de663fdcb

commit 13f72372413400410aaa94b7f0e2ff7de663fdcb
Author: Carl Love <cel@us.ibm.com>
Date:   Wed Jun 22 16:14:20 2022 +0100

    gdb/testsuite: fix gdb.base/break-idempotent.exp on ppc
    
    When running the gdb.base/break-idempotent.exp test on ppc, I was
    seeing some test failures (or rather errors), that looked like this:
    
      (gdb) watch local
      Hardware watchpoint 2: local
    
      has_hw_wp_support: Hardware watchpoint detected
      ERROR: no fileid for gcc2-power8
      ERROR: Couldn't send delete breakpoints to GDB.
      ERROR OCCURED: can't read "gdb_spawn_id": no such variable
          while executing
      "expect {
      -i 1000 -timeout 100
              -re ".*A problem internal to GDB has been detected" {
                  fail "$message (GDB internal error)"
                  gdb_internal_erro..."
          ("uplevel" body line 1)
          invoked from within
    
    What happens is that in break-idempotent.exp we basically do this:
    
        if {[prepare_for_testing "failed to prepare" $binfile $srcfile $opts]} {
            continue
        }
    
        # ....
    
        if {![skip_hw_watchpoint_tests]} {
            test_break $always_inserted "watch"
        }
    
    The problem with this is that skip_hw_watchpoint_tests, includes this:
    
        if { [istarget "i?86-*-*"]
             || [istarget "x86_64-*-*"]
             || [istarget "ia64-*-*"]
             || [istarget "arm*-*-*"]
             || [istarget "aarch64*-*-*"]
             || ([istarget "powerpc*-*-linux*"] && [has_hw_wp_support])
             || [istarget "s390*-*-*"] } {
            return 0
        }
    
    For powerpc only we call has_hw_wp_support.  This is a caching proc
    that runs a test within GDB to detect if we have hardware watchpoint
    support or not.
    
    Unfortunately, to run this test we restart GDB, and when the test has
    completed, we exit GDB.  This means that in break-idempotent.exp, when
    we call skip_hw_watchpoint_tests for the first time on powerpc, GDB
    will unexpectedly be exited.  When we later call delete_breakpoints we
    see the errors I reported above.
    
    The fix is to call skip_hw_watchpoint_tests early, before we start GDB
    as part of the break-idempotent.exp script, and store the result in a
    variable, we can then check this variable in the script as needed.
    
    After this change break-idempotent.exp runs fine on powerpc.
    
    Co-authored-by: Andrew Burgess <aburgess@redhat.com>

Diff:
---
 gdb/testsuite/gdb.base/break-idempotent.exp | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/gdb/testsuite/gdb.base/break-idempotent.exp b/gdb/testsuite/gdb.base/break-idempotent.exp
index 29002f103a8..837ac000b57 100644
--- a/gdb/testsuite/gdb.base/break-idempotent.exp
+++ b/gdb/testsuite/gdb.base/break-idempotent.exp
@@ -36,6 +36,12 @@
 
 standard_testfile
 
+# The skip_hw_watchpoint_tests starts GDB on a small test program to
+# check if HW watchpoints are supported.  We do not want to restart
+# GDB after this test script has itself started GDB, so call
+# skip_hw_watchpoint_tests first and cache the result.
+set skip_hw_watchpoint_tests_p [skip_hw_watchpoint_tests]
+
 # Force a breakpoint re-set in GDB.  Currently this is done by
 # reloading symbols with the "file" command.
 
@@ -174,7 +180,7 @@ foreach_with_prefix pie { "nopie" "pie" } {
 	    test_break $always_inserted "hbreak"
 	}
 
-	if {![skip_hw_watchpoint_tests]} {
+	if {!$skip_hw_watchpoint_tests_p} {
 	    test_break $always_inserted "watch"
 	}