gcc 4.3 on alpha generates wrong code when -foptimize-sibling-calls is used (which is enabled at -O2). It was not the case with gcc 4.2, and this is still reproducible with gcc from trunk from 20090106. This is the reason why most of the complex tests of the glibc testsuite are failing with gcc 4.3.
Here is a reduced testcase: $ cat main.c #include <math.h> #include <complex.h> __complex__ float my_print_complex (__complex__ float x); int main() { __complex__ float a; __real__ a = 9; __imag__ a = 42; my_print_complex(a); return 0; } $ cat print.c #include <complex.h> #include <math.h> #include <stdio.h> __complex__ float internal_print_complex (__complex__ float x) { printf("%f+%fi\n", __real__ x, __imag__ x); if (__real__ x < 0) { __real__ x = -__real__ x; } return x; } __complex__ float my_print_complex (__complex__ float x) { return internal_print_complex (x); } $ gcc-4.3 -Wall -c main.c -o main.o $ gcc-4.3 -O1 -foptimize-sibling-calls -Wall -c print.c -o print.o $ gcc-4.3 -o test main.o print.o $ ./test 0.000000+0.000000i When print.o is not compiled with -foptimize-sibling-calls, the result is: $./test 9.000000+42.000000i $ -- Summary: -foptimize-sibling-calls generates wrong code on alpha Product: gcc Version: 4.3.4 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: aurelien at aurel32 dot net GCC build triplet: alphaev68-unknown-linux-gnu GCC host triplet: alphaev68-unknown-linux-gnu GCC target triplet: alphaev68-unknown-linux-gnu http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38969