[commit/RFC] fix gdb.trace/collection.exp bitrot

[Pedro Alves <pedro@codesourcery.com>]

I was adding a small test to gdb/trace/collection.exp for some
other random tracing bug fix, and noticed that it actually
never ran against gdbserver with tracepoints support.  The
test assumes that after gdb_load, which isn't true for all
board files, or native testing.  It's also not true with
the local gdbserver testing boardfile found in the wiki,
that most people use.  The test was then always being
skipped with that common pattern in gdb.trace/ tests:

 # We generously give ourselves one "pass" if we successfully
 # detect that this test cannot be run on this target!
 if { ![gdb_target_supports_trace] } then {
     pass "Current target does not support trace"
     return 1;
 }

The other bitrot issue fixed by the patch, is, on some
targets, printing $sp prints the pointer type in addition
to the value, like so:

 (top-gdb) p $sp
 $1 = (void *) 0x7fffffffe030

Printing $pc prints even more things:

 (top-gdb) p $pc
 $1 = (void (*)()) 0x456d53 <main+15>

The test isn't expecting this.  The fix is just to 
do "print /x" instead:

 (top-gdb) p /x $sp
 $1 = 0x7fffffffe030

 (top-gdb) p /x $pc
 $1 = 0x456d53

I've applied the patch below to fix these issues.

However, the test still has these FAILs:

 Running ../../../src/gdb/testsuite/gdb.trace/collection.exp ...
 FAIL: gdb.trace/collection.exp: collect args collectively: collected argarray #0
 FAIL: gdb.trace/collection.exp: collect args collectively: collected argarray #1
 FAIL: gdb.trace/collection.exp: collect args collectively: collected argarray #2
 FAIL: gdb.trace/collection.exp: collect args collectively: collected argarray #3
 FAIL: gdb.trace/collection.exp: collect args individually: collected argarray #0
 FAIL: gdb.trace/collection.exp: collect args individually: collected argarray #1
 FAIL: gdb.trace/collection.exp: collect args individually: collected argarray #2
 FAIL: gdb.trace/collection.exp: collect args individually: collected argarray #3
 FAIL: gdb.trace/collection.exp: collect argarray collectively: collected argarray #0
 FAIL: gdb.trace/collection.exp: collect argarray collectively: collected argarray #1
 FAIL: gdb.trace/collection.exp: collect argarray collectively: collected argarray #2
 FAIL: gdb.trace/collection.exp: collect argarray collectively: collected argarray #3
 FAIL: gdb.trace/collection.exp: collect argarray individually: collected argarray #0
 FAIL: gdb.trace/collection.exp: collect argarray individually: collected argarray #1
 FAIL: gdb.trace/collection.exp: collect argarray individually: collected argarray #2
 FAIL: gdb.trace/collection.exp: collect argarray individually: collected argarray #3
 
                 === gdb Summary ===
 
 # of expected passes            361
 # of unexpected failures        16

[to be clear, you can't see these if your gdbserver
doesn't supports tracepoints yet, nor can you see these with
native testing]

All the failures in the test look similar to this:

 print argarray[0]
 Cannot access memory at address 0x7fff138c9aa0
 (gdb) FAIL: gdb.trace/collection.exp: collect args collectively: collected argarray #0

That is, the tracepoint was set to collect the `argarray' argument, of:

 /* Test collecting args. */
 int args_test_func (argc, argi, argf, argd, argstruct, argarray)
      char   argc;
      int    argi;
      float  argf;
      double argd;
      test_struct argstruct;
      int argarray[4];
 {

But, array passing in C is special; even though the argument is
declared like an array, only a pointer to the array passed in.

So, collecting `argarray' only collects the array address, not its
contents.  But, the test tried to print the array's contents, and,
that fails.

The question is.  What to do then?  Should the test just be
fixed to not assume that collecting an array argument, collects
the whole array?  I believe so.

Regular printing also just prints the pointer:

 (gdb) frame
 #0  args_test_func (argc=1 '\001', argi=2, argf=3.29999995, argd=4.4000000000000004, argstruct=...,
     argarray=0x7fffffffe010) at ../../../src/gdb/testsuite/gdb.trace/collection.c:65
 (gdb) p argarray
 $1 = (int *) 0x7fffffffe010
 (gdb) up
 #1  0x0000000000400cb0 in main (argc=1, argv=0x7fffffffe118, envp=0x7fffffffe128)
     at ../../../src/gdb/testsuite/gdb.trace/collection.c:242
 (gdb) p myarray
 $2 = {111, 112, 113, 114}
 (gdb) p &
 $3 = (int (*)[4]) 0x7fffffffe010
 (gdb)

This matches the language semantics.  If the user
wants to collect the array contents, she should do
so explicitly.

I also tried compiling the test with stabs+, just in case and
I see the same.  Maybe it was different at some point.

-- 
Pedro Alves

2010-03-29  Pedro Alves  <pedro@codesourcery.com>

	gdb/testsuite/
	* gdb.trace/collection.exp (executable): New.
	(binfile): Use it.
	(fpreg, spreg, pcreg): New.
	(test_register): Use gdb_test_multiple.  Pass /x to print.
	(prepare_for_trace_test): New.
	(run_trace_experiment): Use "continue", not gdb_run_cmd.
	(gdb_collect_args_test, gdb_collect_argstruct_test)
	(gdb_collect_argarray_test, gdb_collect_locals_test): Use
	prepare_for_trace_test.
	(gdb_collect_registers_test): Use prepare_for_trace_test.  Use
	fpreg, spreg and pcreg.
	(gdb_collect_expression_test, gdb_collect_globals_test): Use
	prepare_for_trace_test.
	(gdb_trace_collection_test): Use fpreg, spreg and pcreg.  Don't
	try to detect tracing support here.  Don't set breakpoints at
	`begin' or `end' here.
	<global scope>: Use clean_restart.  Run to main before checking
	for tracing support.  Check for for tracing support here.

---
 gdb/testsuite/gdb.trace/collection.exp |  143 ++++++++++++++-------------------
 1 file changed, 62 insertions(+), 81 deletions(-)

Index: src/gdb/testsuite/gdb.trace/collection.exp
===================================================================
--- src.orig/gdb/testsuite/gdb.trace/collection.exp	2010-03-28 22:47:37.000000000 +0100
+++ src/gdb/testsuite/gdb.trace/collection.exp	2010-03-28 23:38:28.000000000 +0100
@@ -24,7 +24,8 @@ set bug_id 0
 
 set testfile "collection"
 set srcfile ${testfile}.c
-set binfile $objdir/$subdir/$testfile
+set executable $testfile
+set binfile $objdir/$subdir/$executable
 
 if { [gdb_compile "$srcdir/$subdir/$srcfile" $binfile \
 	executable {debug nowarnings}] != "" } {
@@ -45,6 +46,20 @@ if { [gdb_compile "$srcdir/$subdir/$srcf
 set ws "\[\r\n\t \]+"
 set cr "\[\r\n\]+"
 
+if [istarget "x86_64-*"] then {
+    set fpreg "rbp"
+    set spreg "rsp"
+    set pcreg "rip"
+} elseif [istarget "i?86-*"] then {
+    set fpreg "ebp"
+    set spreg "esp"
+    set pcreg "eip"
+} else {
+    set fpreg "fp"
+    set spreg "sp"
+    set pcreg "pc"
+}
+
 #
 # Utility procs
 #
@@ -53,36 +68,35 @@ proc test_register { reg test_id } {
     global cr
     global gdb_prompt
 
-    send_gdb "print $reg\n"
-    gdb_expect {
-	-re "\\$\[0-9\]+ = \[x0\]+$cr$gdb_prompt " {
+    gdb_test_multiple "print /x $reg" "" {
+	-re "\\$\[0-9\]+ = \[x0\]+$cr$gdb_prompt $" {
 	    fail "collect $test_id: collected $reg (zero)"
 	}
-	-re "\\$\[0-9\]+ = \[x0-9a-fA-F\]+$cr$gdb_prompt " {
+	-re "\\$\[0-9\]+ = \[x0-9a-fA-F\]+$cr$gdb_prompt $" {
 	    pass "collect $test_id: collected $reg"
 	}
-	-re "\[Ee\]rror.*$gdb_prompt " {
+	-re "\[Ee\]rror.*$gdb_prompt $" {
 	    fail "collect $test_id: collected $reg (error)"
 	}
-	timeout {
-	    fail "collect $test_id: collected $reg (timeout)"
-	}
     }
 }
 
+proc prepare_for_trace_test {} {
+    global executable
+
+    clean_restart $executable
+
+    runto_main
+
+    gdb_test "break begin" "" ""
+    gdb_test "break end" "" ""
+}
+
 proc run_trace_experiment { msg test_func } {
-    global gdb_prompt
-    gdb_run_cmd
-    gdb_expect {
-	-re ".*Breakpoint \[0-9\]+, begin .*$gdb_prompt $" { 
-	}
-	-re ".*$gdb_prompt $" { 
-	    fail "collect $msg: advance to go"
-	}
-	timeout { 
-	    fail "collect $msg: advance to go (timeout)"
-	}
-    }
+    gdb_test "continue" \
+	".*Breakpoint \[0-9\]+, begin .*" \
+	"collect $msg: advance to begin"
+
     gdb_test "tstart" \
 	    "\[\r\n\]+" \
 	    "collect $msg: start trace experiment"
@@ -106,10 +120,7 @@ proc gdb_collect_args_test { myargs msg 
     global cr
     global gdb_prompt
 
-    # Make sure we're in a sane starting state.
-    gdb_test "tstop" "" ""
-    gdb_test "tfind none" "" ""
-    gdb_delete_tracepoints
+    prepare_for_trace_test
 
     gdb_test "trace args_test_func" \
 	    "Tracepoint \[0-9\]+ at .*" \
@@ -171,10 +182,7 @@ proc gdb_collect_argstruct_test { myargs
     global cr
     global gdb_prompt
 
-    # Make sure we're in a sane starting state.
-    gdb_test "tstop" "" ""
-    gdb_test "tfind none" "" ""
-    gdb_delete_tracepoints
+    prepare_for_trace_test
 
     gdb_test "trace argstruct_test_func" \
 	    "Tracepoint \[0-9\]+ at .*" \
@@ -210,10 +218,7 @@ proc gdb_collect_argarray_test { myargs 
     global cr
     global gdb_prompt
 
-    # Make sure we're in a sane starting state.
-    gdb_test "tstop" "" ""
-    gdb_test "tfind none" "" ""
-    gdb_delete_tracepoints
+    prepare_for_trace_test
 
     gdb_test "trace argarray_test_func" \
 	    "Tracepoint \[0-9\]+ at .*" \
@@ -249,10 +254,7 @@ proc gdb_collect_locals_test { func mylo
     global cr
     global gdb_prompt
 
-    # Make sure we're in a sane starting state.
-    gdb_test "tstop" "" ""
-    gdb_test "tfind none" "" ""
-    gdb_delete_tracepoints
+    prepare_for_trace_test
 
     # Find the comment-identified line for setting this tracepoint.
     set testline 0
@@ -330,11 +332,11 @@ proc gdb_collect_locals_test { func mylo
 proc gdb_collect_registers_test { myregs } {
     global cr
     global gdb_prompt
+    global fpreg
+    global spreg
+    global pcreg
 
-    # Make sure we're in a sane starting state.
-    gdb_test "tstop" "" ""
-    gdb_test "tfind none" "" ""
-    gdb_delete_tracepoints
+    prepare_for_trace_test
 
     # We'll simply re-use the args_test_function for this test
     gdb_test "trace args_test_func" \
@@ -347,9 +349,9 @@ proc gdb_collect_registers_test { myregs
     # Begin the test.
     run_trace_experiment $myregs args_test_func
 
-    test_register "\$fp" $myregs
-    test_register "\$sp" $myregs
-    test_register "\$pc" $myregs
+    test_register "\$$fpreg" $myregs
+    test_register "\$$spreg" $myregs
+    test_register "\$$pcreg" $myregs
 
     gdb_test "tfind none" \
 	    "#0  end .*" \
@@ -360,10 +362,7 @@ proc gdb_collect_expression_test { func 
     global cr
     global gdb_prompt
 
-    # Make sure we're in a sane starting state.
-    gdb_test "tstop" "" ""
-    gdb_test "tfind none" "" ""
-    gdb_delete_tracepoints
+    prepare_for_trace_test
 
     # Find the comment-identified line for setting this tracepoint.
     set testline 0
@@ -406,10 +405,7 @@ proc gdb_collect_globals_test { } {
     global cr
     global gdb_prompt
 
-    # Make sure we're in a sane starting state.
-    gdb_test "tstop" "" ""
-    gdb_test "tfind none" "" ""
-    gdb_delete_tracepoints
+    prepare_for_trace_test
 
     # Find the comment-identified line for setting this tracepoint.
     set testline 0
@@ -485,21 +481,11 @@ proc gdb_collect_globals_test { } {
 	    "collect globals: cease trace debugging"
 }
 
-proc gdb_trace_collection_test { } {
-    global gdb_prompt;
-
-    gdb_test "set width 0" "" ""
-    delete_breakpoints
-
-    # We generously give ourselves one "pass" if we successfully 
-    # detect that this test cannot be run on this target!
-    if { ![gdb_target_supports_trace] } then { 
-	pass "Current target does not support trace"
-	return 1;
-    }
+proc gdb_trace_collection_test {} {
+    global fpreg
+    global spreg
+    global pcreg
 
-    gdb_test "break begin" "" ""
-    gdb_test "break end"   "" ""
     gdb_collect_args_test "\$args" \
 	    "args collectively"
     gdb_collect_args_test "argc, argi, argf, argd, argstruct, argarray" \
@@ -527,9 +513,8 @@ proc gdb_trace_collection_test { } {
     gdb_collect_locals_test statlocal_test_func \
 	    "locc, loci, locf, locd, locst, locar" \
 	    "static locals individually"
-    
     gdb_collect_registers_test "\$regs"
-    gdb_collect_registers_test "\$fp, \$sp, \$pc"
+    gdb_collect_registers_test "\$$fpreg, \$$spreg, \$$pcreg"
     gdb_collect_globals_test
     
     #
@@ -605,22 +590,18 @@ proc gdb_trace_collection_test { } {
 
 }
 
-# Start with a fresh gdb.
- 
-gdb_exit
-gdb_start
-gdb_reinitialize_dir $srcdir/$subdir
-gdb_load $binfile
- 
-if [target_info exists gdb_stub] {
-    gdb_step_for_stub;
+clean_restart $executable
+runto_main
+
+# We generously give ourselves one "pass" if we successfully
+# detect that this test cannot be run on this target!
+if { ![gdb_target_supports_trace] } then {
+    pass "Current target does not support trace"
+    return 1;
 }
- 
+
 # Body of test encased in a proc so we can return prematurely.
 gdb_trace_collection_test
 
 # Finished!
 gdb_test "tfind none" "" ""
-
-
-