[gcc/devel/c++-coroutines] c++: Handle COMPOUND_EXPRs in get_narrower and warnings_for_convert_and_check [PR91993]
Iain D Sandoe
iains@gcc.gnu.org
Mon Mar 23 20:58:39 GMT 2020
https://gcc.gnu.org/g:ca6c722561ce9b9dc7b59cfd9d29c9b466732721
commit ca6c722561ce9b9dc7b59cfd9d29c9b466732721
Author: Jakub Jelinek <jakub@redhat.com>
Date: Mon Mar 23 19:47:24 2020 +0100
c++: Handle COMPOUND_EXPRs in get_narrower and warnings_for_convert_and_check [PR91993]
As the testcases shows, the -Wconversion warning behaves quite differently
when -fsanitize=undefined vs. when not sanitizing, but in the end it is
not something specific to sanitizing, if a user uses
return static_cast<uc>(static_cast<uc>((d++, a) << 1U) | b) | c;
instead of
return static_cast<uc>(static_cast<uc>(a << 1U) | b) | c;
and thus there is some COMPOUND_EXPR involved, cp_build_binary_op behaves
significantly different, e.g. shorten_binary_op will have different result
(uc for the case without COMPOUND_EXPR, int with it), but it isn't limited
to that.
> 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.
2020-03-23 Jakub Jelinek <jakub@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.
Diff:
---
gcc/ChangeLog | 7 +++++++
gcc/c-family/ChangeLog | 6 ++++++
gcc/c-family/c-warn.c | 5 +++++
gcc/testsuite/ChangeLog | 10 ++++++++++
.../c-c++-common/ubsan/float-cast-overflow-1.c | 2 +-
.../c-c++-common/ubsan/float-cast-overflow-2.c | 2 +-
.../c-c++-common/ubsan/float-cast-overflow-4.c | 2 +-
gcc/testsuite/g++.dg/ubsan/pr91993.C | 17 +++++++++++++++++
gcc/testsuite/g++.dg/warn/Wconversion-pr91993.C | 17 +++++++++++++++++
gcc/tree.c | 15 +++++++++++++++
10 files changed, 80 insertions(+), 3 deletions(-)
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 4509447caa3..9ba58273c21 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2020-03-23 Jakub Jelinek <jakub@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.
+
2020-03-23 Lewis Hyatt <lhyatt@gmail.com>
* opts.c (print_filtered_help): Improve the help text for alias options.
diff --git a/gcc/c-family/ChangeLog b/gcc/c-family/ChangeLog
index 3f195ebcc5d..0d805c64bde 100644
--- a/gcc/c-family/ChangeLog
+++ b/gcc/c-family/ChangeLog
@@ -1,3 +1,9 @@
+2020-03-23 Jakub Jelinek <jakub@redhat.com>
+
+ PR c++/91993
+ * c-warn.c (warnings_for_convert_and_check): For expr and/or
+ result being COMPOUND_EXPRs, skip to ultimate rhs.
+
2020-03-20 Richard Sandiford <richard.sandiford@arm.com>
PR middle-end/94072
diff --git a/gcc/c-family/c-warn.c b/gcc/c-family/c-warn.c
index 9315cac683e..f6b3afc727c 100644
--- a/gcc/c-family/c-warn.c
+++ b/gcc/c-family/c-warn.c
@@ -1359,6 +1359,11 @@ warnings_for_convert_and_check (location_t loc, tree type, tree expr,
{
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);
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index c1ab2bc79bb..1d053e07721 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,13 @@
+2020-03-23 Jakub Jelinek <jakub@redhat.com>
+
+ PR c++/91993
+ * 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.
+
2020-03-23 Srinath Parvathaneni <srinath.parvathaneni@arm.com>
Andre Vieira <andre.simoesdiasvieira@arm.com>
Mihail Ionescu <mihail.ionescu@arm.com>
diff --git a/gcc/testsuite/c-c++-common/ubsan/float-cast-overflow-1.c b/gcc/testsuite/c-c++-common/ubsan/float-cast-overflow-1.c
index 8139cc1723f..6df065fd8f7 100644
--- a/gcc/testsuite/c-c++-common/ubsan/float-cast-overflow-1.c
+++ b/gcc/testsuite/c-c++-common/ubsan/float-cast-overflow-1.c
@@ -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*-*-* } } } } */
diff --git a/gcc/testsuite/c-c++-common/ubsan/float-cast-overflow-2.c b/gcc/testsuite/c-c++-common/ubsan/float-cast-overflow-2.c
index 426c625fc6b..ea685ceaabd 100644
--- a/gcc/testsuite/c-c++-common/ubsan/float-cast-overflow-2.c
+++ b/gcc/testsuite/c-c++-common/ubsan/float-cast-overflow-2.c
@@ -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"
diff --git a/gcc/testsuite/c-c++-common/ubsan/float-cast-overflow-4.c b/gcc/testsuite/c-c++-common/ubsan/float-cast-overflow-4.c
index 48ad257c641..68f85490649 100644
--- a/gcc/testsuite/c-c++-common/ubsan/float-cast-overflow-4.c
+++ b/gcc/testsuite/c-c++-common/ubsan/float-cast-overflow-4.c
@@ -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"
diff --git a/gcc/testsuite/g++.dg/ubsan/pr91993.C b/gcc/testsuite/g++.dg/ubsan/pr91993.C
new file mode 100644
index 00000000000..f903398060a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ubsan/pr91993.C
@@ -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" }
+}
diff --git a/gcc/testsuite/g++.dg/warn/Wconversion-pr91993.C b/gcc/testsuite/g++.dg/warn/Wconversion-pr91993.C
new file mode 100644
index 00000000000..63a8462f9ed
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wconversion-pr91993.C
@@ -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" }
+}
diff --git a/gcc/tree.c b/gcc/tree.c
index ee4519363a7..f38dfffc16e 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -8862,6 +8862,21 @@ get_narrower (tree op, int *unsignedp_ptr)
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
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