The attached C source gives wrong output when compiled with inlined functions
(-O3 or -O2 -finline-functions) with gcc-4.1-20050501 or gcc-4.0.0. Compiling
gives the following warning twice:
dereferencing type-punned pointer will break strict-aliasing rules
The expected output is 0 0, the actual output is two large values. Without
inlined functions or with the unsigned char pointers changed to char pointers
the problem disappears.
There seem to be two problems. One seems to be using an uninitialised stack
value for the pointer which should be initialized to the empty string. The other
seems to be that a pointer (the p2 pointer in the findlast function in the first
inlined readlen call) is modified in a register and is not written back to the
stack before it is read from the stack (to calculate the return value).
On (RedHat modified) gcc 3.4 the output is 0 -1 (it has only the second problem)
and in the actual application there was no problem with gcc 3.3 and before.
--
Summary: wrong-code with inlining and type-punned pointer
Product: gcc
Version: 4.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: rtl-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: gcc at arbruijn dot dds dot nl
CC: gcc-bugs at gcc dot gnu dot org
GCC build triplet: i686-pc-linux-gnu
GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21402
