Author: petdance Date: Mon Dec 17 11:25:23 2007 New Revision: 24013 Modified: trunk/docs/pdds/pdd07_codingstd.pod
Log: added note about checking strcmp() as a boolean Modified: trunk/docs/pdds/pdd07_codingstd.pod ============================================================================== --- trunk/docs/pdds/pdd07_codingstd.pod (original) +++ trunk/docs/pdds/pdd07_codingstd.pod Mon Dec 17 11:25:23 2007 @@ -312,6 +312,14 @@ Do not compare directly against NULL, 0, or FALSE. Instead, write a boolean test, e.g. C<if (!foo) ...>. +However, the sense of the expression being checked must be a boolean. +Specifically, C<strcmp()> and its brethren are three-state returns. + + if ( !strcmp(x,y) ) # BAD, checks for if x and y match, but looks + # like it is checking that they do NOT match. + if ( strcmp(x,y) == 0 ) # GOOD, checks proper return value + if ( STREQ(x,y) ) # GOOD, uses boolean wrapper macro + (Note: C<PMC *> values should be checked for nullity with the C<PMC_IS_NULL> macro, unfortunately leading to violations of the double-negative rule.)
