# [PATCH] banned.h: mark strncat() as banned 3 messages from 2019-01-02 to 2019-01-03. Participants: Eric Wong, Eric Sunshine, Jeff King. Thread: https://gitlist.dev/t/50144 ## Eric Wong, 2019-01-02 09:38 Subject: [PATCH] banned.h: mark strncat() as banned Message-ID: <20190102093846.6664-1-e@80x24.org> URL: https://gitlist.dev/e/20190102093846.6664-1-e%4080x24.org ``` strncat() has the same quadratic behavior as strcat() and is difficult-to-read and bug-prone. While it hasn't yet been a problem in git iself, strncat() found it's way into 'master' of cgit and caused segfaults on my system. Signed-off-by: Eric Wong --- banned.h | 2 ++ 1 file changed, 2 insertions(+) diff --git a/banned.h b/banned.h index 28f5937035..447af24807 100644 --- a/banned.h +++ b/banned.h @@ -16,6 +16,8 @@ #define strcat(x,y) BANNED(strcat) #undef strncpy #define strncpy(x,y,n) BANNED(strncpy) +#undef strncat +#define strncat(x,y,n) BANNED(strncat) #undef sprintf #undef vsprintf -- EW ``` ## Eric Sunshine, 2019-01-02 18:00 Subject: Re: [PATCH] banned.h: mark strncat() as banned Message-ID: URL: https://gitlist.dev/e/CAPig%2BcR2w3S%3D%3D3-zstjmuB9jw4H-aPK7xqMeMLK-P94%3D%2B18jJQ%40mail.gmail.com In-Reply-To: <20190102093846.6664-1-e@80x24.org> ``` On Wed, Jan 2, 2019 at 4:38 AM Eric Wong wrote: > > strncat() has the same quadratic behavior as strcat() and is > difficult-to-read and bug-prone. While it hasn't yet been a > problem in git iself, strncat() found it's way into 'master' s/iself/itself/ > of cgit and caused segfaults on my system. > > Signed-off-by: Eric Wong ``` ## Jeff King, 2019-01-03 04:49 Subject: Re: [PATCH] banned.h: mark strncat() as banned Message-ID: <20190103044941.GA20047@sigill.intra.peff.net> URL: https://gitlist.dev/e/20190103044941.GA20047%40sigill.intra.peff.net In-Reply-To: <20190102093846.6664-1-e@80x24.org> ``` On Wed, Jan 02, 2019 at 09:38:46AM +0000, Eric Wong wrote: > strncat() has the same quadratic behavior as strcat() and is > difficult-to-read and bug-prone. While it hasn't yet been a > problem in git iself, strncat() found it's way into 'master' > of cgit and caused segfaults on my system. I'm in favor of this. It doesn't have the "oops, I didn't NUL-terminate for you" problem that strncpy() has. But it actually has the opposite problem! It will always place a NUL, and you have to feed it sizeof(dst)-1 to avoid an overflow. So I think it's important for safety (though I'd be fine banning it on the quadratic grounds alone ;) ). -Peff ```