On Wed, Mar 18, 2020 at 05:37:26PM -0400, Jason Merrill via Gcc-patches wrote:
> How about improving get_narrower to handle COMPOUND_EXPR? I'd think that
> would do the trick without affecting evaluation order.
Not completely, had to change also warnings_for_convert_and_check, but with
that it works. The float-cast-overflow* changes are needed because now with
-O1+ we emit lots of -Woverflow warnings on the testcase, but we do emit
those warnings on the testcase even when compiling just with -O1 and without
-fsanitize=float-cast-overflow, so it seems to me a change in the right
direction, having -fsanitize= or explicit comma expressions smaller effect
on the warnings that are emitted.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2020-03-20 Jakub Jelinek <ja...@redhat.com>
PR c++/91993
* tree.c (get_narrower): Handle COMPOUND_EXPR by recursing on
ultimate rhs and if returned something different, reconstructing
the COMPOUND_EXPRs.
* c-warn.c (warnings_for_convert_and_check): For expr and/or
result being COMPOUND_EXPRs, skip to ultimate rhs.
* g++.dg/warn/Wconversion-pr91993.C: New test.
* g++.dg/ubsan/pr91993.C: New test.
* c-c++-common/ubsan/float-cast-overflow-1.c: Add -Wno-overflow
to dg-options.
* c-c++-common/ubsan/float-cast-overflow-2.c: Likewise.
* c-c++-common/ubsan/float-cast-overflow-4.c: Likewise.
--- gcc/tree.c.jj 2020-03-17 13:50:52.382941623 +0100
+++ gcc/tree.c 2020-03-19 18:43:18.405499531 +0100
@@ -8862,6 +8862,21 @@ get_narrower (tree op, int *unsignedp_pt
tree win = op;
bool integral_p = INTEGRAL_TYPE_P (TREE_TYPE (op));
+ if (TREE_CODE (op) == COMPOUND_EXPR)
+ {
+ while (TREE_CODE (op) == COMPOUND_EXPR)
+ op = TREE_OPERAND (op, 1);
+ tree ret = get_narrower (op, unsignedp_ptr);
+ if (ret == op)
+ return win;
+ op = win;
+ for (tree *p = &win; TREE_CODE (op) == COMPOUND_EXPR;
+ op = TREE_OPERAND (op, 1), p = &TREE_OPERAND (*p, 1))
+ *p = build2_loc (EXPR_LOCATION (op), COMPOUND_EXPR,
+ TREE_TYPE (ret), TREE_OPERAND (op, 0),
+ ret);
+ return win;
+ }
while (TREE_CODE (op) == NOP_EXPR)
{
int bitschange
--- gcc/c-family/c-warn.c.jj 2020-01-23 19:17:24.072286895 +0100
+++ gcc/c-family/c-warn.c 2020-03-19 19:21:43.389730189 +0100
@@ -1359,6 +1359,11 @@ warnings_for_convert_and_check (location
{
loc = expansion_point_location_if_in_system_header (loc);
+ while (TREE_CODE (expr) == COMPOUND_EXPR)
+ expr = TREE_OPERAND (expr, 1);
+ while (TREE_CODE (result) == COMPOUND_EXPR)
+ result = TREE_OPERAND (result, 1);
+
bool cst = TREE_CODE_CLASS (TREE_CODE (result)) == tcc_constant;
tree exprtype = TREE_TYPE (expr);
--- gcc/testsuite/g++.dg/warn/Wconversion-pr91993.C.jj 2020-03-19
18:21:02.635049452 +0100
+++ gcc/testsuite/g++.dg/warn/Wconversion-pr91993.C 2020-03-19
18:21:02.635049452 +0100
@@ -0,0 +1,17 @@
+// PR c++/91993
+// { dg-do compile }
+// { dg-options "-Wconversion" }
+
+typedef unsigned char uc;
+
+int
+foo (const uc &a, const uc &b, const uc &c)
+{
+ return static_cast<uc>(static_cast<uc>(a << 1U) | b) | c; // {
dg-bogus "conversion from 'int' to 'unsigned char' may change value" }
+}
+
+int
+bar (const uc &a, const uc &b, const uc &c, int &d)
+{
+ return static_cast<uc>(static_cast<uc>((d++, a) << 1U) | b) | c; // {
dg-bogus "conversion from 'int' to 'unsigned char' may change value" }
+}
--- gcc/testsuite/g++.dg/ubsan/pr91993.C.jj 2020-03-19 18:21:02.635049452
+0100
+++ gcc/testsuite/g++.dg/ubsan/pr91993.C 2020-03-19 18:21:02.635049452
+0100
@@ -0,0 +1,17 @@
+// PR c++/91993
+// { dg-do compile }
+// { dg-options "-Wconversion -fsanitize=undefined" }
+
+typedef unsigned char uc;
+
+int
+foo (const uc &a, const uc &b, const uc &c)
+{
+ return static_cast<uc>(static_cast<uc>(a << 1U) | b) | c; // {
dg-bogus "conversion from 'int' to 'unsigned char' may change value" }
+}
+
+int
+bar (const uc &a, const uc &b, const uc &c, int &d)
+{
+ return static_cast<uc>(static_cast<uc>((d++, a) << 1U) | b) | c; // {
dg-bogus "conversion from 'int' to 'unsigned char' may change value" }
+}
--- gcc/testsuite/c-c++-common/ubsan/float-cast-overflow-1.c.jj 2020-01-12
11:54:37.029404115 +0100
+++ gcc/testsuite/c-c++-common/ubsan/float-cast-overflow-1.c 2020-03-20
00:40:57.403648603 +0100
@@ -1,5 +1,5 @@
/* { dg-do run { target { lp64 || ilp32 } } } */
-/* { dg-options "-fsanitize=float-cast-overflow" } */
+/* { dg-options "-fsanitize=float-cast-overflow -Wno-overflow" } */
/* { dg-additional-options "-ffloat-store" { target { ia32 } } } */
/* { dg-additional-options "-mieee" { target { { alpha*-*-* } || { sh*-*-* } }
} } */
--- gcc/testsuite/c-c++-common/ubsan/float-cast-overflow-2.c.jj 2020-01-12
11:54:37.029404115 +0100
+++ gcc/testsuite/c-c++-common/ubsan/float-cast-overflow-2.c 2020-03-20
00:41:21.757289152 +0100
@@ -1,6 +1,6 @@
/* { dg-do run } */
/* { dg-require-effective-target int128 } */
-/* { dg-options "-fsanitize=float-cast-overflow" } */
+/* { dg-options "-fsanitize=float-cast-overflow -Wno-overflow" } */
#include "float-cast.h"
--- gcc/testsuite/c-c++-common/ubsan/float-cast-overflow-4.c.jj 2020-01-12
11:54:37.029404115 +0100
+++ gcc/testsuite/c-c++-common/ubsan/float-cast-overflow-4.c 2020-03-20
00:41:32.053137185 +0100
@@ -1,5 +1,5 @@
/* { dg-do run { target { lp64 } } } */
-/* { dg-options "-fsanitize=float-cast-overflow" } */
+/* { dg-options "-fsanitize=float-cast-overflow -Wno-overflow" } */
#include <limits.h>
#include "float-cast.h"
Jakub
