(see attached testcases; testcase.c shows the problem, testcase2.c shows that
reorging the code works around it)
it appears that gcc does not realize that after
if (variable < 1 || variable > 10)
return -1;
the "variable" is in the range [1..10], likely because the execution of the
second check is optional due to the ||.
in a typical __builtin_object_size() scenario, like
if (__builtin_object_size(foo) < variable)
some_error();
where foo is 10 bytes in size, this means the check does not get optimized out.
--
Summary: gcc does not optimize a case that it should to make
__builtin_object_size() more useful
Product: gcc
Version: 4.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: arjan at linux dot intel dot com
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41477
