* [PATCH] Use strlen instead of sizeof on char* string @ 2012-11-13 15:47 Alexander Stein 2012-11-13 20:26 ` Marc Kleine-Budde 0 siblings, 1 reply; 6+ messages in thread From: Alexander Stein @ 2012-11-13 15:47 UTC (permalink / raw) To: linux-can; +Cc: Alexander Stein This bug was detected by the clang warning: libsocketcan.c:384:16: warning: argument to 'sizeof' in 'strncmp' call is the same expression as the source; did you mean to provide an explicit length? [-Wsizeof-pointer-memaccess] sizeof(name)) != 0) ~~~~~~~^~~~~~ Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com> --- src/libsocketcan.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/src/libsocketcan.c b/src/libsocketcan.c index fedcbdc..3ad2a6c 100644 --- a/src/libsocketcan.c +++ b/src/libsocketcan.c @@ -364,6 +364,7 @@ static int do_get_nl_link(int fd, __u8 acquire, const char *name, void *res) nl_msg = NLMSG_NEXT(nl_msg, u_msglen)) { int type = nl_msg->nlmsg_type; int len; + int namelen = strlen(name); if (type == NLMSG_DONE) { done++; @@ -381,7 +382,7 @@ static int do_get_nl_link(int fd, __u8 acquire, const char *name, void *res) if (strncmp ((char *)RTA_DATA(tb[IFLA_IFNAME]), name, - sizeof(name)) != 0) + namelen) != 0) continue; if (tb[IFLA_LINKINFO]) -- 1.7.8.6 ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] Use strlen instead of sizeof on char* string 2012-11-13 15:47 [PATCH] Use strlen instead of sizeof on char* string Alexander Stein @ 2012-11-13 20:26 ` Marc Kleine-Budde 2012-11-14 8:55 ` [PATCH] Use strcmp instead of strncmp Kurt Van Dijck 0 siblings, 1 reply; 6+ messages in thread From: Marc Kleine-Budde @ 2012-11-13 20:26 UTC (permalink / raw) To: Alexander Stein; +Cc: linux-can [-- Attachment #1: Type: text/plain, Size: 1680 bytes --] On 11/13/2012 04:47 PM, Alexander Stein wrote: > This bug was detected by the clang warning: > libsocketcan.c:384:16: warning: argument to 'sizeof' in 'strncmp' call > is the same expression as the source; did you mean to provide an > explicit length? [-Wsizeof-pointer-memaccess] > sizeof(name)) != 0) > ~~~~~~~^~~~~~ > > Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com> > --- > src/libsocketcan.c | 3 ++- > 1 files changed, 2 insertions(+), 1 deletions(-) > > diff --git a/src/libsocketcan.c b/src/libsocketcan.c > index fedcbdc..3ad2a6c 100644 > --- a/src/libsocketcan.c > +++ b/src/libsocketcan.c > @@ -364,6 +364,7 @@ static int do_get_nl_link(int fd, __u8 acquire, const char *name, void *res) > nl_msg = NLMSG_NEXT(nl_msg, u_msglen)) { > int type = nl_msg->nlmsg_type; > int len; > + int namelen = strlen(name); > > if (type == NLMSG_DONE) { > done++; > @@ -381,7 +382,7 @@ static int do_get_nl_link(int fd, __u8 acquire, const char *name, void *res) > > if (strncmp > ((char *)RTA_DATA(tb[IFLA_IFNAME]), name, > - sizeof(name)) != 0) > + namelen) != 0) What about using strcmp() instead. AFAIK it will compare until it finds the end of the string in one of the strings, so it should be no difference here? > continue; > > if (tb[IFLA_LINKINFO]) > Marc -- Pengutronix e.K. | Marc Kleine-Budde | Industrial Linux Solutions | Phone: +49-231-2826-924 | Vertretung West/Dortmund | Fax: +49-5121-206917-5555 | Amtsgericht Hildesheim, HRA 2686 | http://www.pengutronix.de | [-- Attachment #2: OpenPGP digital signature --] [-- Type: application/pgp-signature, Size: 259 bytes --] ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Use strcmp instead of strncmp 2012-11-13 20:26 ` Marc Kleine-Budde @ 2012-11-14 8:55 ` Kurt Van Dijck 2012-11-14 9:07 ` Alexander Stein 0 siblings, 1 reply; 6+ messages in thread From: Kurt Van Dijck @ 2012-11-14 8:55 UTC (permalink / raw) To: Marc Kleine-Budde; +Cc: Alexander Stein, linux-can On Tue, Nov 13, 2012 at 09:26:50PM +0100, Marc Kleine-Budde wrote: > On 11/13/2012 04:47 PM, Alexander Stein wrote: > > This bug was detected by the clang warning: > > libsocketcan.c:384:16: warning: argument to 'sizeof' in 'strncmp' call > > is the same expression as the source; did you mean to provide an > > explicit length? [-Wsizeof-pointer-memaccess] > > sizeof(name)) != 0) > > ~~~~~~~^~~~~~ strlen() requires a null terminator. Is that always present? Unfortunately, I've no access to the libsocketcan code today... > > > > Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com> > > --- > > src/libsocketcan.c | 3 ++- > > 1 files changed, 2 insertions(+), 1 deletions(-) > > > > diff --git a/src/libsocketcan.c b/src/libsocketcan.c > > index fedcbdc..3ad2a6c 100644 > > --- a/src/libsocketcan.c > > +++ b/src/libsocketcan.c > > @@ -364,6 +364,7 @@ static int do_get_nl_link(int fd, __u8 acquire, const char *name, void *res) > > nl_msg = NLMSG_NEXT(nl_msg, u_msglen)) { > > int type = nl_msg->nlmsg_type; > > int len; > > + int namelen = strlen(name); > > > > if (type == NLMSG_DONE) { > > done++; > > @@ -381,7 +382,7 @@ static int do_get_nl_link(int fd, __u8 acquire, const char *name, void *res) > > > > if (strncmp > > ((char *)RTA_DATA(tb[IFLA_IFNAME]), name, > > - sizeof(name)) != 0) > > + namelen) != 0) > > What about using strcmp() instead. AFAIK it will compare until it finds > the end of the string in one of the strings, so it should be no > difference here? if name contains a null terminator, using strcmp() is even better. > > > continue; > > > > if (tb[IFLA_LINKINFO]) > > > > Marc > > -- > Pengutronix e.K. | Marc Kleine-Budde | > Industrial Linux Solutions | Phone: +49-231-2826-924 | > Vertretung West/Dortmund | Fax: +49-5121-206917-5555 | > Amtsgericht Hildesheim, HRA 2686 | http://www.pengutronix.de | > ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Use strcmp instead of strncmp 2012-11-14 8:55 ` [PATCH] Use strcmp instead of strncmp Kurt Van Dijck @ 2012-11-14 9:07 ` Alexander Stein 2012-11-14 10:04 ` Kurt Van Dijck 0 siblings, 1 reply; 6+ messages in thread From: Alexander Stein @ 2012-11-14 9:07 UTC (permalink / raw) To: Kurt Van Dijck; +Cc: Marc Kleine-Budde, linux-can Hello, On Wednesday 14 November 2012 09:55:37, Kurt Van Dijck wrote: > On Tue, Nov 13, 2012 at 09:26:50PM +0100, Marc Kleine-Budde wrote: > > On 11/13/2012 04:47 PM, Alexander Stein wrote: > > > This bug was detected by the clang warning: > > > libsocketcan.c:384:16: warning: argument to 'sizeof' in 'strncmp' call > > > is the same expression as the source; did you mean to provide an > > > explicit length? [-Wsizeof-pointer-memaccess] > > > sizeof(name)) != 0) > > > ~~~~~~~^~~~~~ > strlen() requires a null terminator. Is that always present? > Unfortunately, I've no access to the libsocketcan code today... > > > > > > Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com> > > > --- > > > src/libsocketcan.c | 3 ++- > > > 1 files changed, 2 insertions(+), 1 deletions(-) > > > > > > diff --git a/src/libsocketcan.c b/src/libsocketcan.c > > > index fedcbdc..3ad2a6c 100644 > > > --- a/src/libsocketcan.c > > > +++ b/src/libsocketcan.c > > > @@ -364,6 +364,7 @@ static int do_get_nl_link(int fd, __u8 acquire, const char *name, void *res) > > > nl_msg = NLMSG_NEXT(nl_msg, u_msglen)) { > > > int type = nl_msg->nlmsg_type; > > > int len; > > > + int namelen = strlen(name); > > > > > > if (type == NLMSG_DONE) { > > > done++; > > > @@ -381,7 +382,7 @@ static int do_get_nl_link(int fd, __u8 acquire, const char *name, void *res) > > > > > > if (strncmp > > > ((char *)RTA_DATA(tb[IFLA_IFNAME]), name, > > > - sizeof(name)) != 0) > > > + namelen) != 0) > > > > What about using strcmp() instead. AFAIK it will compare until it finds > > the end of the string in one of the strings, so it should be no > > difference here? > if name contains a null terminator, using strcmp() is even better. name is passed directly from public API functions like can_get_state. So the user has to provide the null terminator. As this cannot be garuanteed it might better to use strlen on (char *)RTA_DATA(tb[IFLA_IFNAME]). BTW: there is no need to introduce a new variable. sizeof can simply be replaced by strlen. Best regards, Alexander ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Use strcmp instead of strncmp 2012-11-14 9:07 ` Alexander Stein @ 2012-11-14 10:04 ` Kurt Van Dijck 2012-11-14 10:10 ` Marc Kleine-Budde 0 siblings, 1 reply; 6+ messages in thread From: Kurt Van Dijck @ 2012-11-14 10:04 UTC (permalink / raw) To: Alexander Stein; +Cc: Marc Kleine-Budde, linux-can On Wed, Nov 14, 2012 at 10:07:15AM +0100, Alexander Stein wrote: > Hello, > > On Wednesday 14 November 2012 09:55:37, Kurt Van Dijck wrote: > > On Tue, Nov 13, 2012 at 09:26:50PM +0100, Marc Kleine-Budde wrote: > > > On 11/13/2012 04:47 PM, Alexander Stein wrote: > > > > This bug was detected by the clang warning: > > > > libsocketcan.c:384:16: warning: argument to 'sizeof' in 'strncmp' call > > > > is the same expression as the source; did you mean to provide an > > > > explicit length? [-Wsizeof-pointer-memaccess] > > > > sizeof(name)) != 0) > > > > ~~~~~~~^~~~~~ > > strlen() requires a null terminator. Is that always present? > > Unfortunately, I've no access to the libsocketcan code today... > > > > > > > > Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com> > > > > --- > > > > src/libsocketcan.c | 3 ++- > > > > 1 files changed, 2 insertions(+), 1 deletions(-) > > > > > > > > diff --git a/src/libsocketcan.c b/src/libsocketcan.c > > > > index fedcbdc..3ad2a6c 100644 > > > > --- a/src/libsocketcan.c > > > > +++ b/src/libsocketcan.c > > > > @@ -364,6 +364,7 @@ static int do_get_nl_link(int fd, __u8 acquire, > const char *name, void *res) > > > > nl_msg = NLMSG_NEXT(nl_msg, u_msglen)) { > > > > int type = nl_msg->nlmsg_type; > > > > int len; > > > > + int namelen = strlen(name); > > > > > > > > if (type == NLMSG_DONE) { > > > > done++; > > > > @@ -381,7 +382,7 @@ static int do_get_nl_link(int fd, __u8 acquire, > const char *name, void *res) > > > > > > > > if (strncmp > > > > ((char *)RTA_DATA(tb[IFLA_IFNAME]), name, > > > > - sizeof(name)) != 0) > > > > + namelen) != 0) > > > > > > What about using strcmp() instead. AFAIK it will compare until it finds > > > the end of the string in one of the strings, so it should be no > > > difference here? > > if name contains a null terminator, using strcmp() is even better. > > name is passed directly from public API functions like can_get_state. So the > user has to provide the null terminator. As this cannot be garuanteed I think we should assume that the user passes a null terminated string. Otherwise, we must question if the user passes a valid address. I don't like to go that way. strcmp() will just work. Kind regards, Kurt ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Use strcmp instead of strncmp 2012-11-14 10:04 ` Kurt Van Dijck @ 2012-11-14 10:10 ` Marc Kleine-Budde 0 siblings, 0 replies; 6+ messages in thread From: Marc Kleine-Budde @ 2012-11-14 10:10 UTC (permalink / raw) To: Alexander Stein, linux-can [-- Attachment #1: Type: text/plain, Size: 2621 bytes --] On 11/14/2012 11:04 AM, Kurt Van Dijck wrote: > On Wed, Nov 14, 2012 at 10:07:15AM +0100, Alexander Stein wrote: >> Hello, >> >> On Wednesday 14 November 2012 09:55:37, Kurt Van Dijck wrote: >>> On Tue, Nov 13, 2012 at 09:26:50PM +0100, Marc Kleine-Budde wrote: >>>> On 11/13/2012 04:47 PM, Alexander Stein wrote: >>>>> This bug was detected by the clang warning: >>>>> libsocketcan.c:384:16: warning: argument to 'sizeof' in 'strncmp' call >>>>> is the same expression as the source; did you mean to provide an >>>>> explicit length? [-Wsizeof-pointer-memaccess] >>>>> sizeof(name)) != 0) >>>>> ~~~~~~~^~~~~~ >>> strlen() requires a null terminator. Is that always present? >>> Unfortunately, I've no access to the libsocketcan code today... >>>>> >>>>> Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com> >>>>> --- >>>>> src/libsocketcan.c | 3 ++- >>>>> 1 files changed, 2 insertions(+), 1 deletions(-) >>>>> >>>>> diff --git a/src/libsocketcan.c b/src/libsocketcan.c >>>>> index fedcbdc..3ad2a6c 100644 >>>>> --- a/src/libsocketcan.c >>>>> +++ b/src/libsocketcan.c >>>>> @@ -364,6 +364,7 @@ static int do_get_nl_link(int fd, __u8 acquire, >> const char *name, void *res) >>>>> nl_msg = NLMSG_NEXT(nl_msg, u_msglen)) { >>>>> int type = nl_msg->nlmsg_type; >>>>> int len; >>>>> + int namelen = strlen(name); >>>>> >>>>> if (type == NLMSG_DONE) { >>>>> done++; >>>>> @@ -381,7 +382,7 @@ static int do_get_nl_link(int fd, __u8 acquire, >> const char *name, void *res) >>>>> >>>>> if (strncmp >>>>> ((char *)RTA_DATA(tb[IFLA_IFNAME]), name, >>>>> - sizeof(name)) != 0) >>>>> + namelen) != 0) >>>> >>>> What about using strcmp() instead. AFAIK it will compare until it finds >>>> the end of the string in one of the strings, so it should be no >>>> difference here? >>> if name contains a null terminator, using strcmp() is even better. >> >> name is passed directly from public API functions like can_get_state. So the >> user has to provide the null terminator. As this cannot be garuanteed > I think we should assume that the user passes a null terminated string. > Otherwise, we must question if the user passes a valid address. I don't > like to go that way. > > strcmp() will just work. +1 Marc -- Pengutronix e.K. | Marc Kleine-Budde | Industrial Linux Solutions | Phone: +49-231-2826-924 | Vertretung West/Dortmund | Fax: +49-5121-206917-5555 | Amtsgericht Hildesheim, HRA 2686 | http://www.pengutronix.de | [-- Attachment #2: OpenPGP digital signature --] [-- Type: application/pgp-signature, Size: 259 bytes --] ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2012-11-14 10:10 UTC | newest] Thread overview: 6+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2012-11-13 15:47 [PATCH] Use strlen instead of sizeof on char* string Alexander Stein 2012-11-13 20:26 ` Marc Kleine-Budde 2012-11-14 8:55 ` [PATCH] Use strcmp instead of strncmp Kurt Van Dijck 2012-11-14 9:07 ` Alexander Stein 2012-11-14 10:04 ` Kurt Van Dijck 2012-11-14 10:10 ` Marc Kleine-Budde
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