------- Comment #3 from gcc at twistedsquare dot com 2009-01-21 17:36 ------- The main optimisation that seems to affect this example, is, -fstrict-overflow. So to reiterate:
Works: gcc gccbug.c -std=gnu99 -O1 Doesn't work: gcc gccbug.c -std=gnu99 -O2 Doesn't work: gcc gccbug.c -std=gnu99 -O2 -fno-strict-overflow Works: gcc gccbug.c -O2 -std=gnu99 -O2 -fno-strict-overflow -fno-tree-vrp I can see that the assumptions involved in strict-overflow may cause the overflow test to behave differently, but it is still the case that under the optimisations, one printf says -128 for the int8_t value, and the other (when passed in the same value from a different call) says 128, and therefore I am still confident that this is a bug. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38929
