From: Ruslan Kabatsayev <b7.10110111@gmail.com>
To: gdb-patches@sourceware.org
Cc: Ruslan Kabatsayev <b7.10110111@gmail.com>
Subject: [PATCH][RFC] Avoid indexing std::vector past the end
Date: Thu, 28 Dec 2017 16:01:00 -0000 [thread overview]
Message-ID: <1514476903-5206-1-git-send-email-b7.10110111@gmail.com> (raw)
Hello all,
On my system I have added some asserts into GCC's stl_vector.h, which check for
various mistakes like out of bounds access, call to std::vector::front on empty
vector etc. to debug my own projects. After I built GDB with such
modifications, I've noticed that in some cases it accesses some vectors out of
bound, namely element one past the end. Effectively the code is something like
`auto*p=&someVector[someVector.size()];`, which, although may seem legitimate
on the first glance since it simply takes address, is still Undefined Behavior
according to the C++ Standard (see e.g. [1] and links in that page).
So I wonder whether GDB deliberately exploits undefined behavior here knowing
that GCC might give(?) some guarantee that this will always work as intended,
or it's simply a mistake, and my patch would be OK.
[1]: https://stackoverflow.com/a/27069592/673852
Regards,
Ruslan
---
gdb/psymtab.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/gdb/psymtab.c b/gdb/psymtab.c
index c87ef25..c622f4c 100644
--- a/gdb/psymtab.c
+++ b/gdb/psymtab.c
@@ -1337,21 +1337,21 @@ recursively_search_psymtabs
}
partial_symbol **gbound
- = &objfile->global_psymbols[ps->globals_offset + ps->n_global_syms];
+ = objfile->global_psymbols.data() + ps->globals_offset + ps->n_global_syms;
partial_symbol **sbound
- = &objfile->static_psymbols[ps->statics_offset + ps->n_static_syms];
+ = objfile->static_psymbols.data() + ps->statics_offset + ps->n_static_syms;
partial_symbol **bound = gbound;
/* Go through all of the symbols stored in a partial
symtab in one loop. */
- partial_symbol **psym = &objfile->global_psymbols[ps->globals_offset];
+ partial_symbol **psym = objfile->global_psymbols.data() + ps->globals_offset;
while (keep_going)
{
if (psym >= bound)
{
if (bound == gbound && ps->n_static_syms != 0)
{
- psym = &objfile->static_psymbols[ps->statics_offset];
+ psym = objfile->static_psymbols.data() + ps->statics_offset;
bound = sbound;
}
else
--
1.9.1
next reply other threads:[~2017-12-28 16:01 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-28 16:01 Ruslan Kabatsayev [this message]
2017-12-30 0:51 ` Simon Marchi
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