Re: [RFA/testsuite] attach.exp: Add small delay in busy loop...

[Joel Brobecker <brobecker@gnat.com>]

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Hello,

On Tue, Nov 18, 2003 at 04:26:07PM -0800, Michael Snyder wrote:
> >2003-11-18  J. Brobecker  <brobecker@gnat.com>
> >
> >        * gdb.base/attach.c: Add small delay in busy loop.
> >        * gdb.base/attach.exp: Make some associated adjustments.
> >
> >OK to apply?
> 
> Seems to work on Linux.  I'd sure like to see that backtrace test,
> though, to confirm that we are able to build a meaningful machine
> state after we attach.

Here is a new version of the patch, with the backtraces in. I do have
two FAILs though. The first FAIL comes from the following test:

   gdb_test "backtrace" \
            ".*in nanosleep ().*in small_delay ().*in main ().*" \
            "backtrace after attach2"

The logs show:

        backtrace
        #0  0x400eb3b5 in ?? () from /lib/libc.so.6
        #1  0x08048412 in small_delay () at ./gdb.base/attach.c:18
        #2  0x08048435 in main () at ./gdb.base/attach.c:29
        (gdb) FAIL: gdb.base/attach.exp: backtrace after attach2

So the problem is that GDB is unable to find the function name for
frame $0. I think this comes from these warnings while performing
the attach command:

        attach 3671
        Attaching to process 3671
        Reading symbols from /[...]/testsuite/gdb.base/attach...done.
  -->   Symbols already loaded for /lib/libm.so.6
  -->   Symbols already loaded for /lib/libc.so.6
        Symbols already loaded for /lib/ld-linux.so.2
        0x400eb3b5 in ?? () from /lib/libc.so.6^M 
        (gdb) PASS: gdb.base/attach.exp: attach2

The second FAIL is identical.

I am not sure what's best to do. Normally, the first purpose when I
wrote the test was to make sure that we were able to see a frame
for procedure main(), and then got overzealous by checking that we
could see at least main(), small_delay() and nanosleep(). But then
this problem came up. In my opinion, we should still keep my zealous
version of the expected output for the "backtrace" commands and either
leave with the fail, or make them as KFAILS (or whatever proper state
it should be, I didn't much follow that discussion).

There is another thing that I think needs mentioning. I noticed I am
the first one to introduce the use of nanosleep(). I think it's pretty
portable, but I am having doubts. Does anybody know if it's not available
on any platform. How about cygwin for instance?

Otherwise, is there another function that I could use instead? Sleep is
used in several of the tests - although the timer resolution is much
coarser, it would probably be fine to use sleep() in this test too.
There is also select, but I'm not sure it's available on cygwin. It's
already been used in one of the pthread examples, though...

-- 
Joel

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Index: attach.c
===================================================================
RCS file: /cvs/src/src/gdb/testsuite/gdb.base/attach.c,v
retrieving revision 1.1.1.1
diff -u -p -r1.1.1.1 attach.c
--- attach.c	28 Jun 1999 23:02:40 -0000	1.1.1.1
+++ attach.c	20 Nov 2003 06:17:45 -0000
@@ -5,15 +5,28 @@
    exit unless/until gdb sets the variable to non-zero.)
    */
 #include <stdio.h>
+#include <time.h>
 
 int  should_exit = 0;
 
+/* Wait for 0.1 sec.  */
+
+void
+small_delay ()
+{
+  const struct timespec ts = { 0, 1000000 }; /* 0.1 sec */
+  nanosleep (&ts, NULL);
+}
+
 int main ()
 {
   int  local_i = 0;
 
   while (! should_exit)
     {
+      /* Insert a small delay in order to avoid consuming all the CPU
+         while waiting for the debugger to take control.  */
+      small_delay ();
       local_i++;
     }
   return 0;
Index: attach.exp
===================================================================
RCS file: /cvs/src/src/gdb/testsuite/gdb.base/attach.exp,v
retrieving revision 1.12
diff -u -p -r1.12 attach.exp
--- attach.exp	7 Aug 2003 17:55:41 -0000	1.12
+++ attach.exp	20 Nov 2003 06:17:45 -0000
@@ -173,12 +173,16 @@ proc do_attach_tests {} {
 
    send_gdb "attach $testpid\n"
    gdb_expect {
-      -re "Attaching to program.*`?$escapedbinfile'?, process $testpid.*main.*at .*$srcfile:.*$gdb_prompt $"\
+      -re "Attaching to program.*`?$escapedbinfile'?, process $testpid.*$gdb_prompt $"\
                       {pass "attach1, after setting file"}
       -re "$gdb_prompt $" {fail "attach1, after setting file"}
       timeout         {fail "(timeout) attach1, after setting file"}
    }
 
+   gdb_test "backtrace" \
+            ".*in nanosleep ().*in small_delay ().*in main ().*" \
+            "backtrace after attach1"
+
    # Verify that we can "see" the variable "should_exit" in the
    # program, and that it is zero.
    #
@@ -236,12 +240,16 @@ proc do_attach_tests {} {
    #
    send_gdb "attach $testpid\n"
    gdb_expect {
-      -re "Attaching to process $testpid.*Reading symbols from $escapedbinfile.*main.*at .*$gdb_prompt $"\
+      -re "Attaching to process $testpid.*Reading symbols from $escapedbinfile.*$gdb_prompt $"\
                       {pass "attach2"}
       -re "$gdb_prompt $" {fail "attach2"}
       timeout         {fail "(timeout) attach2"}
    }
 
+   gdb_test "backtrace" \
+            ".*in nanosleep ().*in small_delay ().*in main ().*" \
+            "backtrace after attach2"
+
    # Verify that we can modify the variable "should_exit" in the
    # program.
    #
@@ -253,16 +261,16 @@ proc do_attach_tests {} {
 
    # Verify that the modification really happened.
    #
-   send_gdb "tbreak 19\n"
+   send_gdb "tbreak 32\n"
    gdb_expect {
-      -re "Breakpoint .*at.*$srcfile, line 19.*$gdb_prompt $"\
+      -re "Breakpoint .*at.*$srcfile, line 32.*$gdb_prompt $"\
                       {pass "after attach2, set tbreak postloop"}
       -re "$gdb_prompt $" {fail "after attach2, set tbreak postloop"}
       timeout         {fail "(timeout) after attach2, set tbreak postloop"}
    }
    send_gdb "continue\n"
    gdb_expect {
-      -re "main.*at.*$srcfile:19.*$gdb_prompt $"\
+      -re "main.*at.*$srcfile:32.*$gdb_prompt $"\
                       {pass "after attach2, reach tbreak postloop"}
       -re "$gdb_prompt $" {fail "after attach2, reach tbreak postloop"}
       timeout         {fail "(timeout) after attach2, reach tbreak postloop"}
@@ -337,11 +345,15 @@ proc do_attach_tests {} {
 
    send_gdb "attach $testpid\n"
    gdb_expect {
-      -re "Attaching to process $testpid.*Reading symbols from $escapedbinfile.*main.*at .*$gdb_prompt $"\
+      -re "Attaching to process $testpid.*Reading symbols from $escapedbinfile.*$gdb_prompt $"\
                       {pass "attach when process' a.out not in cwd"}
       -re "$gdb_prompt $" {fail "attach when process' a.out not in cwd"}
       timeout         {fail "(timeout) attach when process' a.out not in cwd"}
    }
+
+   gdb_test "backtrace" \
+            ".*in nanosleep ().*in small_delay ().*in main ().*" \
+            "backtrace after attach when process' a.out not in cwd"
 
    send_gdb "kill\n"
    gdb_expect {