On (02/10/14 22:51), Sumit Bose wrote:
On Thu, Oct 02, 2014 at 10:20:56PM +0200, Lukas Slebodnik wrote:
> On (02/10/14 15:12), Simo Sorce wrote:
> >On Thu, 2 Oct 2014 19:33:02 +0200
> >Lukas Slebodnik <lslebodn(a)redhat.com> wrote:
> >
> >> ehlo,
> >>
> >> There is a warning with some version of gcc (4.9.1, 4.4.7).
> >> Warning is not visible with gcc 4.8
> >> In my opinion, variable "a" should be initialized every time if
> >> "maps" is not NULL.
> >
> >I agree that "a" should be intialized every time, in fact I do not
> >agree with your patch where you set it to be a volatile, it is not.
> >
> >The main issue here is that the name and way this variable is used is
> >confusing.
> >
> >A better way would be to define a locally in the first loop, and in the
> >function define a better name initialized to a negative value.
> >
> >the name should probably be called something like base_attr_idx and
> >intialized as:
> >
> >int base_attr_idx = 0;
> >
> >and if the first part of the code finds the base_attr it is looking for
> >it would simply assing a to it (note we do away with "a" completely).
> >
> >if (map) {
> > for (i = 1; i < attrs_num; i++) {
> > ...
> > }
> > if (i < attrs_num) {
> > store = true;
> > base_attr_idx = i;
> > ...
> > }
> >}
> >
> >then the second for loop where you get the error would be change to:
> >for (ai = base_attr_idx; ai > 0 && ai < attrs_num; ai++) {
> >
> I suppose you meant similar patch
> diff --git a/src/providers/ldap/sdap.c b/src/providers/ldap/sdap.c
> index 7034b11..6e8b16e 100644
> --- a/src/providers/ldap/sdap.c
> +++ b/src/providers/ldap/sdap.c
> @@ -305,6 +305,7 @@ int sdap_parse_entry(TALLOC_CTX *memctx,
> char *str;
> int lerrno;
> int a, i, ret, ai;
> + int base_attr_idx;
> const char *name;
> bool store;
> bool base64;
> @@ -412,6 +413,7 @@ int sdap_parse_entry(TALLOC_CTX *memctx,
> /* interesting attr */
> if (a < attrs_num) {
> store = true;
> + base_attr_idx = a;
> name = map[a].sys_name;
> if (strcmp(name, SYSDB_SSH_PUBKEY) == 0) {
> base64 = true;
> @@ -478,7 +480,7 @@ int sdap_parse_entry(TALLOC_CTX *memctx,
> * attrs in case there is a map. Find all that match
> * and copy the value
> */
> - for (ai = a; ai < attrs_num; ai++) {
> + for (ai = base_attr_idx; ai < attrs_num; ai++) {
> /* check if this attr is valid with the chosen
> * schema */
> if (!map[ai].name) continue;
>
>
> It didn't help.
> src/providers/ldap/sdap.c: In function 'sdap_parse_entry':
> src/providers/ldap/sdap.c:308:9: error: 'base_attr_idx' may be used
uninitialized in this function [-Werror=maybe-uninitialized]
> int base_attr_idx;
> ^
> cc1: all warnings being treated as errors
> (BTW: There is no difference between using a and base_attr_idx)
>
> Any other better solution is welcomed.
Just a wild guess. Maybe the compiler is doing some wild optimizations
assuming that attrs_num might be 1, 0 or even smaller. Does it help to
check for (map && num_attrs > 1) ? (I would try myself, but I do not
have the right gcc version at hand)
It didn't help either.
Compiler do some kind of non obvious optimisation with variable "a" or with
simo's proprosed variable "base_attr_idx".
Suppressing optimization with keyword volatile fixes a warning.
I would like to have better solution, but I cannot find any.
LS