From patchwork Thu Aug 26 18:38:49 2010 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [4/5] HACKING: add string management rules Date: Thu, 26 Aug 2010 08:38:49 -0000 From: Blue Swirl X-Patchwork-Id: 62802 Message-Id: To: qemu-devel Add string management rules, somewhat like libvirt HACKING. Signed-off-by: Blue Swirl --- HACKING | 24 ++++++++++++++++++++++++ 1 files changed, 24 insertions(+), 0 deletions(-) diff --git a/HACKING b/HACKING index 554009e..a3d714f 100644 --- a/HACKING +++ b/HACKING @@ -83,3 +83,27 @@ qemu_vmalloc/qemu_memalign/qemu_vfree APIs. Memory allocated by qemu_vmalloc or qemu_memalign must be freed with qemu_vfree, since breaking this will cause problems on Win32 and user emulators. + +4. String manipulation + +Do not use the strncpy function. According to the man page, it does +*not* guarantee a NULL-terminated buffer, which makes it extremely dangerous +to use. Instead, use functionally equivalent function: +void pstrcpy(char *buf, int buf_size, const char *str) + +Don't use strcat because it can't check for buffer overflows, but: +char *pstrcat(char *buf, int buf_size, const char *s) + +The same limitation exists with sprintf and vsprintf, so use snprintf and +vsnprintf. + +QEMU provides other useful string functions: +int strstart(const char *str, const char *val, const char **ptr) +int stristart(const char *str, const char *val, const char **ptr) +int qemu_strnlen(const char *s, int max_len) + +There are also replacement character processing macros for isxyz and toxyz, +so instead of e.g. isalnum you should use qemu_isalnum. + +Because of the memory management rules, you must use qemu_strdup/qemu_strndup +instead of plain strdup/strndup.