GCC 4.8 introduced aggressive loop optimizations which will break some loops if the code has undefined behavior. We have previously reported that gcc should output a warning in this case and that fix is included in WR 6.0.0.16. We have however discovered a new case in which aggressive loop optimizations will break a loop without issuing a warning. The attached code contains a function which removes an item from a list and moves down all trailing items. The expected result is a shorter list but when the optimization is activated, the size of the list is not decreased. The example is compiled with “i686-wrs-linux-gnu-gcc --sysroot <sysroot> -m32 -Wall -O3 -o loop loop.c” and the problem goes away when adding “-fno-aggressive-loop-optimizations”. The behavior is the same when compiling for ARM. We consider it a bug that no compiler warning is shown in this example. Expected output: 4 items Item 0: 1 Item 1: 2 Item 2: 3 Item 3: 4 3 items Item 0: 2 Item 1: 3 Item 2: 4 Actual output: 4 items Item 0: 1 Item 1: 2 Item 2: 3 Item 3: 4 4 items Item 0: 2 Item 1: 3 Item 2: 4 Item 3: 4
