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From: "xdje42 at gmail dot com" <sourceware-bugzilla@sourceware.org>
To: gdb-prs@sourceware.org
Subject: [Bug python/18175] New: gdb.parse_and_eval should un-lazy results
Date: Sun, 29 Mar 2015 21:52:00 -0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=18175

            Bug ID: 18175
           Summary: gdb.parse_and_eval should un-lazy results
           Product: gdb
           Version: HEAD
            Status: NEW
          Severity: normal
          Priority: P2
         Component: python
          Assignee: unassigned at sourceware dot org
          Reporter: xdje42 at gmail dot com

gdb.parse_and_eval should un-lazy its results.

Otherwise the following can happen.

Try 1:

(gdb) py foo = gdb.parse_and_eval ("*(char*) $sp")
(gdb) x/b $sp
0x7fffffffe1c0: 0
(gdb) py print foo
0 '\000'
(gdb) set *(char*) $sp = 42
(gdb) x/b $sp
0x7fffffffe1c0: 42
(gdb) py print foo
0 '\000' <<<<< expected result

Try 2:

(gdb) py foo = gdb.parse_and_eval ("*(char*) $sp")
(gdb) set *(char*) $sp = 43
(gdb) py print foo
43 '+' <<<<< Ugh.
(gdb) 

Note that in the first example, the "py print foo" before modifying
memory is sufficient to un-lazy the value.
I point this out to show that if we don't make this change then
debugging such things can be nasty: a simple "print" can modify
program behaviour.

Guile's parse-and-eval has the same issue.

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