git/list[1] front-page[2] threads[3] people[4] search[5] about
 

Re: avoid atoi, when possible; int overflow -> heap corruption

From
Jim Meyering <jim@meyering.net>
Date
May 22, 2006, 13:31 UTC
Message-ID
<878xoufaof.fsf@rho.meyering.net>
In-Reply-To
<118833cc0605220616t75a182b1oa404d5efe8a1f5d9@mail.gmail.com>
"Morten Welinder" <mwelinder@gmail.com> wrote:
Show 8 quoted lines
>> There are about 20 uses of atoi, and most calls can return
>> a usable result in spite of an invalid input -- just because
>> atoi returns the same thing for "99" as "99-and-any-suffix".
>> It would be better not to ignore invalid inputs.
>
> atoi has undefined behaviour for "99-and-any-suffix".  You might
> get lucky and get back 99, but you might also get a random value
> or a core dump.

I've never heard of that. POSIX says that atoi(str) is equivalent to:

    (int) strtol(str, (char **)NULL, 10)
    except that the handling of errors may differ.
    If the value cannot be represented, the behavior is undefined.

Since strtol works fine with such a suffix, and since 99 can be represented, I don't see why there would be any undefined behavior.

Do you know of an implementation for which `atoi ("99-and-any-suffix")' does anything other than return 99?

Previous: Morten WelinderNext: Jeff King
Message 17 of 20 in “synchronizing incremental git changes to cvs”
  1. Jim MeyeringMay 20, 2006
  2. Johannes SchindelinMay 20, 2006
  3. Jim MeyeringMay 21, 2006
  4. Pavel RoskinMay 22, 2006
  5. Jakub NarebskiMay 22, 2006
  6. Martin LanghoffMay 21, 2006
  7. Jim MeyeringMay 21, 2006
  8. Junio C HamanoMay 21, 2006
  9. Jim MeyeringMay 21, 2006
  10. don't accept bogus N in `HEAD~N'Jim Meyering, May 21, 2006
  11. Jakub NarebskiMay 21, 2006
  12. Jim MeyeringMay 22, 2006
  13. Junio C HamanoMay 22, 2006
  14. Junio C HamanoMay 22, 2006
  15. avoid atoi, when possible; int overflow -> heap corruptionJim Meyering, May 22, 2006
  16. Morten WelinderMay 22, 2006
  17. Jim MeyeringMay 22, 2006
  18. Jeff KingMay 22, 2006
  19. Morten WelinderMay 22, 2006
  20. detect write failure, even for stdoutJim Meyering, May 22, 2006

Read the whole thread, see it on lore, or plain text.

$ cat FOOTERMessages come from the public archive at lore.kernel.org/git, fetched every hour. The front page is chosen and written each morning by an AI editor and can be wrong; the threads themselves are the record. About and API. For agents: an MCP server at https://gitlist.dev/mcp, and any thread, story or person page as Markdown by adding .md to its URL (or sending Accept: text/markdown). Details in /llms.txt.