Re: [PATCH] testsuite: Avoid a buffer overrun in `gdb.base/maint.exp'

[Pedro Alves <palves at redhat dot com>]

On 10/19/2016 08:07 PM, Maciej W. Rozycki wrote:

>  I've looked into adjusting the size of the buffer dynamically as the 
> `full_buffer' condition triggers and in principle it appears doable with 
> the tools TCL and `expect' provide and no need to bend backwards to get it 
> done, however it seems to require more than just a trivial intervention in 
> `gdb_test_multiple', so I have decided to leave it for the next time the 
> issue triggers.  Maybe it won't.
> 
>  Needless to say, this change has passed `mips-mti-linux-gnu' regression 
> testing.  OK to apply?

I saw this too yesterday after fixing:

 https://sourceware.org/ml/gdb-patches/2016-10/msg00786.html

but came up with a different fix.  This one does not require growing
the buffer dynamically.  We instead parse output as is comes, with
exp_continue, which should fix the problem for good.

WDYT?

>From d4ac077aa309cc3816ad0dd0cc9c0ef2d91cd7fc Mon Sep 17 00:00:00 2001
From: Pedro Alves <palves@redhat.com>
Date: Fri, 28 Oct 2016 12:03:18 +0100
Subject: [PATCH] gdb/testsuite: Avoid a buffer overrun in `gdb.base/maint.exp'

Fixes:

 PASS: gdb.base/maint.exp: maint w/o args
 ERROR: internal buffer is full.
 UNRESOLVED: gdb.base/maint.exp: maint info line-table w/o a file name

The problem is just many symtabs and long line tables, enough to
overflow the expect buffer.  Fix this by matching input incrementally.

gdb/testsuite/ChangeLog:
yyyy-mm-dd  Pedro Alves  <palves@redhat.com>

	* gdb.base/maint.exp <maint info line-table w/o a file name>: Use
	gdb_test_multiple, tighten regexps and match symtabs and line
	tables incrementally.
---
 gdb/testsuite/gdb.base/maint.exp | 38 +++++++++++++++++++++++++++++++++++---
 1 file changed, 35 insertions(+), 3 deletions(-)

diff --git a/gdb/testsuite/gdb.base/maint.exp b/gdb/testsuite/gdb.base/maint.exp
index e66f566..b07b370 100644
--- a/gdb/testsuite/gdb.base/maint.exp
+++ b/gdb/testsuite/gdb.base/maint.exp
@@ -474,9 +474,41 @@ gdb_test "maint" \
     "\"maintenance\" must be followed by the name of a maintenance command\\.\r\nList.*unambiguous\\..*" \
     "maint w/o args"
 
-gdb_test "maint info line-table" \
-    "symtab: \[^\n\r\]+${srcfile}.*\\(\\(struct symtab \\*\\) $hex\\)\r\nlinetable: \\(\\(struct linetable \\*\\) $hex\\):\r\nINDEX.*LINE.*ADDRESS.*" \
-    "maint info line-table w/o a file name"
+# Test that "main info line-table" w/o a file name shows the symtab for
+# $srcfile.
+set saw_srcfile 0
+set test "maint info line-table w/o a file name"
+gdb_test_multiple "maint info line-table" $test {
+    -re "symtab: \[^\n\r\]+${srcfile} \\(\\(struct symtab \\*\\) $hex\\)\r\nlinetable: \\(\\(struct linetable \\*\\) $hex\\):\r\nINDEX\[ \t\]+LINE\[ \t\]+ADDRESS" {
+	set saw_srcfile 1
+	exp_continue
+    }
+    -re "symtab: \[^\n\r\]+ \\(\\(struct symtab \\*\\) $hex\\)\r\nlinetable: \\(\\(struct linetable \\*\\) $hex\\):\r\nINDEX\[ \t\]+LINE\[ \t\]+ADDRESS" {
+	# Match each symtab to avoid overflowing expect's buffer.
+	exp_continue
+    }
+    -re "$decimal\[ \t\]+$decimal\[ \t\]+$hex\r\n" {
+	# Line table entries can be long too:
+	#
+	#  INDEX    LINE ADDRESS
+	#  0          29 0x00000000004006f6
+	#  1          30 0x00000000004006fa
+	#  2          31 0x0000000000400704
+	#  3          42 0x0000000000400706
+	#  4          43 0x0000000000400719
+	#  5          44 0x0000000000400722
+	#  6          45 0x0000000000400740
+	#  (...)
+	#  454       129 0x00007ffff7df1d28
+	#  455         0 0x00007ffff7df1d3f
+	#
+	# Match each line to avoid overflowing expect's buffer.
+	exp_continue
+    }
+    -re "$gdb_prompt $" {
+	gdb_assert $saw_srcfile $test
+    }
+}
 
 gdb_test "maint info line-table ${srcfile}" \
     "symtab: \[^\n\r\]+${srcfile}.*INDEX.*LINE.*ADDRESS.*" \
-- 
2.5.5