[obv] Code cleanup: Move print_command_1 expr variable scope

[obv] Code cleanup: Move print_command_1 expr variable scope

[Jan Kratochvil]

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From: Jan Kratochvil <jan.kratochvil@redhat.com>
Subject: [PATCH] Code cleanup: Move print_command_1 expr variable scope
Date: Thu, 26 Mar 2015 18:44:38 +0100

gdb/ChangeLog
2015-03-26  Jan Kratochvil  <jan.kratochvil@redhat.com>

	Code cleanup.
	* printcmd.c (print_command_1): Move expr variable scope.
---
 gdb/ChangeLog  | 5 +++++
 gdb/printcmd.c | 3 ++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 55a8383..94ef5c8 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,6 +1,11 @@
 2015-03-26  Jan Kratochvil  <jan.kratochvil@redhat.com>
 
 	Code cleanup.
+	* printcmd.c (print_command_1): Move expr variable scope.
+
+2015-03-26  Jan Kratochvil  <jan.kratochvil@redhat.com>
+
+	Code cleanup.
 	* printcmd.c (validate_format): Make the parameter cmdname const.
 
 2015-03-26  Don Breazeal  <donb@codesourcery.com>
diff --git a/gdb/printcmd.c b/gdb/printcmd.c
index deb501a..a1451f8 100644
--- a/gdb/printcmd.c
+++ b/gdb/printcmd.c
@@ -946,7 +946,6 @@ validate_format (struct format_data fmt, const char *cmdname)
 static void
 print_command_1 (const char *exp, int voidprint)
 {
-  struct expression *expr;
   struct cleanup *old_chain = make_cleanup (null_cleanup, NULL);
   char format = 0;
   struct value *val;
@@ -969,6 +968,8 @@ print_command_1 (const char *exp, int voidprint)
 
   if (exp && *exp)
     {
+      struct expression *expr;
+
       expr = parse_expression (exp);
       make_cleanup (free_current_contents, &expr);
       val = evaluate_expression (expr);
-- 
2.3.4

Re: [obv] Code cleanup: Move print_command_1 expr variable scope

[Simon Marchi]

Hi Jan,

I think this patch is wrong. Starting with that commit (f30d5c7),
some tests (e.g. mi-break.exp) started to fail for me, because
of gdb segfaulting. Backtrace here: http://paste.ubuntu.com/10690836/

The address of expr is passed to the cleanup. When the cleanup is ran,
expr is no longer in scope, so what is at that address is probably not
safe to use anymore. That's my guess.

Simon

Revert: [obv] Code cleanup: Move print_command_1 expr variable scope

[Jan Kratochvil]

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Hi Simon,

On Fri, 27 Mar 2015 20:15:13 +0100, Simon Marchi wrote:
> I think this patch is wrong. Starting with that commit (f30d5c7),
> some tests (e.g. mi-break.exp) started to fail for me, because
> of gdb segfaulting. Backtrace here: http://paste.ubuntu.com/10690836/
> 
> The address of expr is passed to the cleanup. When the cleanup is ran,
> expr is no longer in scope, so what is at that address is probably not
> safe to use anymore. That's my guess.

yes, you are sure right, I have reverted it now.

Sorry I made that commit somehow automatically, not expecting it may have any
side effects.


Thanks,
Jan

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From: Jan Kratochvil <jan.kratochvil@redhat.com>
Subject: [PATCH] Revert: Code cleanup: Move print_command_1 expr variable scope
Date: Fri, 27 Mar 2015 20:19:37 +0100

Simon Marchi:

I think this patch is wrong. Starting with that commit (f30d5c7),
some tests (e.g. mi-break.exp) started to fail for me, because
of gdb segfaulting.

The address of expr is passed to the cleanup. When the cleanup is ran,
expr is no longer in scope, so what is at that address is probably not
safe to use anymore. That's my guess.

gdb/ChangeLog
2015-03-27  Jan Kratochvil  <jan.kratochvil@redhat.com>

	Revert:
	2015-03-26  Jan Kratochvil  <jan.kratochvil@redhat.com>
	Code cleanup.
	* printcmd.c (print_command_1): Move expr variable scope.
---
 gdb/ChangeLog  | 7 +++++++
 gdb/printcmd.c | 3 +--
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 72940b0..6c6b94e 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,10 @@
+2015-03-27  Jan Kratochvil  <jan.kratochvil@redhat.com>
+
+	Revert:
+	2015-03-26  Jan Kratochvil  <jan.kratochvil@redhat.com>
+	Code cleanup.
+	* printcmd.c (print_command_1): Move expr variable scope.
+
 2015-03-27  Joel Brobecker  <brobecker@adacore.com>
 
 	* dtrace-probe.c (dtrace_process_dof_probe): Initialize expr to NULL.
diff --git a/gdb/printcmd.c b/gdb/printcmd.c
index a1451f8..deb501a 100644
--- a/gdb/printcmd.c
+++ b/gdb/printcmd.c
@@ -946,6 +946,7 @@ validate_format (struct format_data fmt, const char *cmdname)
 static void
 print_command_1 (const char *exp, int voidprint)
 {
+  struct expression *expr;
   struct cleanup *old_chain = make_cleanup (null_cleanup, NULL);
   char format = 0;
   struct value *val;
@@ -968,8 +969,6 @@ print_command_1 (const char *exp, int voidprint)
 
   if (exp && *exp)
     {
-      struct expression *expr;
-
       expr = parse_expression (exp);
       make_cleanup (free_current_contents, &expr);
       val = evaluate_expression (expr);
-- 
2.1.0

Re: Revert: [obv] Code cleanup: Move print_command_1 expr variable scope

[Simon Marchi]

On 15-03-27 03:22 PM, Jan Kratochvil wrote:
> Hi Simon,
> 
> On Fri, 27 Mar 2015 20:15:13 +0100, Simon Marchi wrote:
>> I think this patch is wrong. Starting with that commit (f30d5c7),
>> some tests (e.g. mi-break.exp) started to fail for me, because
>> of gdb segfaulting. Backtrace here: http://paste.ubuntu.com/10690836/
>>
>> The address of expr is passed to the cleanup. When the cleanup is ran,
>> expr is no longer in scope, so what is at that address is probably not
>> safe to use anymore. That's my guess.
> 
> yes, you are sure right, I have reverted it now.
> 
> Sorry I made that commit somehow automatically, not expecting it may have any
> side effects.

I would have done the same. I must say I was very surprised when git bisect
told me that was the culprit. Very very sneaky bug...


> Thanks,
> Jan
>