From 2786c0221b65b443217c7709cbc51e96db1b87e1 Mon Sep 17 00:00:00 2001 From: Stefan Schulze Frielinghaus Date: Sun, 26 Apr 2020 17:10:51 +0200 Subject: var-tracking.c: Fix possible use of uninitialized variable pre While bootstrapping GCC on S/390 the following warning/error is raised: gcc/var-tracking.c:10239:34: error: 'pre' may be used uninitialized in this function [-Werror=maybe-uninitialized] 10239 | VTI (bb)->out.stack_adjust += pre; | ^ The lines of interest are: HOST_WIDE_INT pre, post = 0; // ... if (!frame_pointer_needed) { insn_stack_adjust_offset_pre_post (insn, &pre, &post); // ... } // ... adjust_insn (bb, insn); if (!frame_pointer_needed && pre) VTI (bb)->out.stack_adjust += pre; Both if statements depend on global variable frame_pointer_needed. In function insn_stack_adjust_offset_pre_post local variable pre is initialized. The problematic part is the function call between both if statements. Since adjust_insn also calls functions which are defined in a different compilation unit, we are not able to prove that global variable frame_pointer_needed is not altered by adjust_insn and its siblings. Thus we must assume that frame_pointer_needed may be true before the call and false afterwards which renders the warning true (admitted the location hint is not totally perfect). By initialising pre we silence the warning. gcc/ChangeLog: 2020-04-30 Stefan Schulze Frielinghaus * var-tracking.c (vt_initialize): Move variables pre and post into inner block and initialize both in order to fix warning about uninitialized use. Remove unnecessary checks for frame_pointer_needed. --- gcc/ChangeLog | 7 +++++++ gcc/var-tracking.c | 7 ++++--- 2 files changed, 11 insertions(+), 3 deletions(-) diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 8abb4c0eda4..563d42cc694 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,10 @@ +2020-04-30 Stefan Schulze Frielinghaus + + * var-tracking.c (vt_initialize): Move variables pre and post + into inner block and initialize both in order to fix warning + about uninitialized use. Remove unnecessary checks for + frame_pointer_needed. + 2020-04-30 Stefan Schulze Frielinghaus * toplev.c (output_stack_usage_1): Ensure that first diff --git a/gcc/var-tracking.c b/gcc/var-tracking.c index 0d39326aa63..fc861a0d8ce 100644 --- a/gcc/var-tracking.c +++ b/gcc/var-tracking.c @@ -10171,7 +10171,6 @@ vt_initialize (void) FOR_EACH_BB_FN (bb, cfun) { rtx_insn *insn; - HOST_WIDE_INT pre, post = 0; basic_block first_bb, last_bb; if (MAY_HAVE_DEBUG_BIND_INSNS) @@ -10216,6 +10215,8 @@ vt_initialize (void) { if (INSN_P (insn)) { + HOST_WIDE_INT pre = 0, post = 0; + if (!frame_pointer_needed) { insn_stack_adjust_offset_pre_post (insn, &pre, &post); @@ -10235,7 +10236,7 @@ vt_initialize (void) cselib_hook_called = false; adjust_insn (bb, insn); - if (!frame_pointer_needed && pre) + if (pre) VTI (bb)->out.stack_adjust += pre; if (DEBUG_MARKER_INSN_P (insn)) @@ -10262,7 +10263,7 @@ vt_initialize (void) add_with_sets (insn, 0, 0); cancel_changes (0); - if (!frame_pointer_needed && post) + if (post) { micro_operation mo; mo.type = MO_ADJUST; -- cgit v1.2.3