| Message ID | 4A607185.6020302@gmail.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
On Friday 17 July 2009, Roel Kluin wrote: > With `sizeof(string) - 1` strncpy() will null terminate the string. No, it won't. See the 'Warning' part of the strncpy man page. > Signed-off-by: Roel Kluin <roel.kluin@gmail.com> > --- > To test this: > > #include <stdio.h> > #include <string.h> > > char a[10]; > char b[10]; > > int main() > { > const char* str = "0123456789012"; > strncpy(a, str, sizeof(a)); > strncpy(b, str, sizeof(b) - 1); > printf("String a was %s, b was %s\n", a, b); > > return 0; > } > > Output: > String a was 0123456789012345678, b was 012345678 This is an invalid test case, it relies on b being zero-filled by the compiler, which is not true for programs in general. > diff --git a/arch/powerpc/platforms/cell/celleb_setup.c b/arch/powerpc/platforms/cell/celleb_setup.c > index 07c234f..cfdbadb 100644 > --- a/arch/powerpc/platforms/cell/celleb_setup.c > +++ b/arch/powerpc/platforms/cell/celleb_setup.c > @@ -80,7 +80,7 @@ static void celleb_show_cpuinfo(struct seq_file *m) > > static int __init celleb_machine_type_hack(char *ptr) > { > - strncpy(celleb_machine_type, ptr, sizeof(celleb_machine_type)); > + strncpy(celleb_machine_type, ptr, sizeof(celleb_machine_type) - 1); > celleb_machine_type[sizeof(celleb_machine_type)-1] = 0; > return 0; > } See the line after the strncpy. This is still required for proper zero-termination. Your patch tries to address a problem that doesn't exist, and does not have any effect at all after celleb_machine_type_hack has completed. Arnd <><
>> With `sizeof(string) - 1` strncpy() will null terminate the string. > > No, it won't. > See the line after the strncpy. This is still required for proper zero-termination. You're right, sorry for the noise. Roel
diff --git a/arch/powerpc/platforms/cell/celleb_setup.c b/arch/powerpc/platforms/cell/celleb_setup.c index 07c234f..cfdbadb 100644 --- a/arch/powerpc/platforms/cell/celleb_setup.c +++ b/arch/powerpc/platforms/cell/celleb_setup.c @@ -80,7 +80,7 @@ static void celleb_show_cpuinfo(struct seq_file *m) static int __init celleb_machine_type_hack(char *ptr) { - strncpy(celleb_machine_type, ptr, sizeof(celleb_machine_type)); + strncpy(celleb_machine_type, ptr, sizeof(celleb_machine_type) - 1); celleb_machine_type[sizeof(celleb_machine_type)-1] = 0; return 0; }
With `sizeof(string) - 1` strncpy() will null terminate the string. Signed-off-by: Roel Kluin <roel.kluin@gmail.com> --- To test this: #include <stdio.h> #include <string.h> char a[10]; char b[10]; int main() { const char* str = "0123456789012"; strncpy(a, str, sizeof(a)); strncpy(b, str, sizeof(b) - 1); printf("String a was %s, b was %s\n", a, b); return 0; } Output: String a was 0123456789012345678, b was 012345678