A r131535 of trunk bootstrapped with --enable-langugages=c --enable-checking=release,valgrind shows this indication for several test-cases, the first being tmpdir-gcc.dg-struct-layout-1/t001 c_compat_x_tst.o compile (just the first indication of several identical is shown): Executing on host: /tmp/hptest8/obj/gcc/xgcc -B/tmp/hptest8/obj/gcc/ -w -I/tmp/hptest8/gcc/gcc/testsuite/gcc.dg/compat -fno-show -column -c -o c_compat_x_tst.o /tmp/hptest8/obj/gcc/testsuite/gcc/gcc.dg-struct-layout-1//t001_x.c (timeout = 300) ==22344== Conditional jump or move depends on uninitialised value(s) ==22344== at 0x7046E2: merge_classes (i386.c:3558) ==22344== by 0x7082A0: classify_argument (i386.c:3682) ==22344== by 0x7083F5: examine_argument (i386.c:3883) ==22344== by 0x708660: ix86_return_in_memory (i386.c:4752) ==22344== by 0x5F3178: default_return_in_memory (targhooks.c:113) ==22344== by 0x52A419: aggregate_value_p (function.c:1801) ==22344== by 0x543704: gimplify_modify_expr_rhs (gimplify.c:3653) ==22344== by 0x53D616: gimplify_modify_expr (gimplify.c:3857) ==22344== by 0x53ED72: gimplify_expr (gimplify.c:5680) ==22344== by 0x541086: gimplify_and_add (gimplify.c:348) ==22344== by 0x53D37C: internal_get_tmp_var (gimplify.c:631) ==22344== by 0x53DF74: gimplify_expr (gimplify.c:6245)
Using a later revision is recommended, at least >= r131589.
merge_classes() itself is clear, so the problem must be in the caller.
It was later reported as PR/38781 and fixed. No valgrind errors here with r146637. *** This bug has been marked as a duplicate of 38781 ***