From e1f45bea2741c271efbc4c2f9dfad93cbcd644c0 Mon Sep 17 00:00:00 2001
From: "Jose E. Marchesi" <jose.marchesi@oracle.com>
Date: Thu, 17 Aug 2023 15:36:26 +0200
Subject: [PATCH] Add warning options -W[no-]compare-distinct-pointer-types
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
GCC emits pedwarns unconditionally when comparing pointers of
different types, for example:
int xdp_context (struct xdp_md *xdp)
{
void *data = (void *)(long)xdp->data;
__u32 *metadata = (void *)(long)xdp->data_meta;
__u32 ret;
if (metadata + 1 > data)
return 0;
return 1;
}
/home/jemarch/foo.c: In function ‘xdp_context’:
/home/jemarch/foo.c:15:20: warning: comparison of distinct pointer types lacks a cast
15 | if (metadata + 1 > data)
| ^
LLVM supports an option -W[no-]compare-distinct-pointer-types that can
be used in order to enable or disable the emission of such warnings.
It is enabled by default.
This patch adds the same options to GCC.
Documentation and testsuite updated included.
Regtested in x86_64-linu-gnu.
No regressions observed.
gcc/ChangeLog:
PR c/106537
* doc/invoke.texi (Option Summary): Mention
-Wcompare-distinct-pointer-types under `Warning Options'.
(Warning Options): Document -Wcompare-distinct-pointer-types.
gcc/c-family/ChangeLog:
PR c/106537
* c.opt (Wcompare-distinct-pointer-types): New option.
gcc/c/ChangeLog:
PR c/106537
* c-typeck.cc (build_binary_op): Warning on comparing distinct
pointer types only when -Wcompare-distinct-pointer-types.
gcc/testsuite/ChangeLog:
PR c/106537
* gcc.c-torture/compile/pr106537-1.c: New test.
* gcc.c-torture/compile/pr106537-2.c: Likewise.
* gcc.c-torture/compile/pr106537-3.c: Likewise.
---
gcc/c-family/c.opt | 4 +++
gcc/c/c-typeck.cc | 6 ++--
gcc/doc/invoke.texi | 6 ++++
.../gcc.c-torture/compile/pr106537-1.c | 34 +++++++++++++++++++
.../gcc.c-torture/compile/pr106537-2.c | 32 +++++++++++++++++
.../gcc.c-torture/compile/pr106537-3.c | 32 +++++++++++++++++
6 files changed, 111 insertions(+), 3 deletions(-)
create mode 100644 gcc/testsuite/gcc.c-torture/compile/pr106537-1.c
create mode 100644 gcc/testsuite/gcc.c-torture/compile/pr106537-2.c
create mode 100644 gcc/testsuite/gcc.c-torture/compile/pr106537-3.c
diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index c7b567ba7abd..2242524cd3e2 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -1935,6 +1935,10 @@ Winvalid-imported-macros
C++ ObjC++ Var(warn_imported_macros) Warning
Warn about macros that have conflicting header units definitions.
+Wcompare-distinct-pointer-types
+C ObjC Var(warn_compare_distinct_pointer_types) Warning Init(1)
+Warn if pointers of distinct types are compared without a cast.
+
flang-info-include-translate
C++ Var(note_include_translate_yes)
Note #include directives translated to import declarations.
diff --git a/gcc/c/c-typeck.cc b/gcc/c/c-typeck.cc
index 6f2fff51683a..e6ddf37d4120 100644
--- a/gcc/c/c-typeck.cc
+++ b/gcc/c/c-typeck.cc
@@ -12772,7 +12772,7 @@ build_binary_op (location_t location, enum tree_code code,
else
/* Avoid warning about the volatile ObjC EH puts on decls. */
if (!objc_ok)
- pedwarn (location, 0,
+ pedwarn (location, OPT_Wcompare_distinct_pointer_types,
"comparison of distinct pointer types lacks a cast");
if (result_type == NULL_TREE)
@@ -12912,8 +12912,8 @@ build_binary_op (location_t location, enum tree_code code,
int qual = ENCODE_QUAL_ADDR_SPACE (as_common);
result_type = build_pointer_type
(build_qualified_type (void_type_node, qual));
- pedwarn (location, 0,
- "comparison of distinct pointer types lacks a cast");
+ pedwarn (location, OPT_Wcompare_distinct_pointer_types,
+ "comparison of distinct pointer types lacks a cast");
}
}
else if (code0 == POINTER_TYPE && null_pointer_constant_p (orig_op1))
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 3380ed8bd6f9..01aa9efebce5 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -345,6 +345,7 @@ Objective-C and Objective-C++ Dialects}.
-Wcast-align -Wcast-align=strict -Wcast-function-type -Wcast-qual
-Wchar-subscripts
-Wclobbered -Wcomment
+-Wcompare-distinct-pointer-types
-Wno-complain-wrong-lang
-Wconversion -Wno-coverage-mismatch -Wno-cpp
-Wdangling-else -Wdangling-pointer -Wdangling-pointer=@var{n}
@@ -9106,6 +9107,11 @@ The latter front end diagnoses
@samp{f951: Warning: command-line option '-fno-rtti' is valid for C++/D/ObjC++ but not for Fortran},
which may be disabled with @option{-Wno-complain-wrong-lang}.
+@opindex Wcompare-distinct-pointer-types
+@item -Wcompare-distinct-pointer-types @r{(C and Objective-C only)}
+Warn if pointers of distinct types are compared without a cast. This
+warning is enabled by default.
+
@opindex Wconversion
@opindex Wno-conversion
@item -Wconversion
diff --git a/gcc/testsuite/gcc.c-torture/compile/pr106537-1.c b/gcc/testsuite/gcc.c-torture/compile/pr106537-1.c
new file mode 100644
index 000000000000..3f3b06577d52
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/compile/pr106537-1.c
@@ -0,0 +1,34 @@
+/* { dg-do compile }
+ { dg-options "-O0" }
+ This testcase checks that warn_compare_distinct_pointer_types is enabled by
+ default. */
+
+typedef int __u32;
+
+struct xdp_md
+{
+ char *data;
+ char *data_meta;
+};
+
+int xdp_context (struct xdp_md *xdp)
+{
+ void *data = (void *)(long)xdp->data;
+ __u32 *metadata = (void *)(long)xdp->data_meta;
+ __u32 ret;
+
+ if (metadata + 1 > data) /* { dg-warning "comparison of distinct pointer types" } */
+ return 1;
+ if (metadata + 1 >= data) /* { dg-warning "comparison of distinct pointer types" } */
+ return 2;
+ if (metadata + 1 < data) /* { dg-warning "comparison of distinct pointer types" } */
+ return 3;
+ if (metadata + 1 <= data) /* { dg-warning "comparison of distinct pointer types" } */
+ return 4;
+ if (metadata + 1 == data) /* { dg-warning "comparison of distinct pointer types" } */
+ return 5;
+ if (metadata + 1 != data) /* { dg-warning "comparison of distinct pointer types" } */
+ return 5;
+
+ return 1;
+}
diff --git a/gcc/testsuite/gcc.c-torture/compile/pr106537-2.c b/gcc/testsuite/gcc.c-torture/compile/pr106537-2.c
new file mode 100644
index 000000000000..6876adf3aab1
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/compile/pr106537-2.c
@@ -0,0 +1,32 @@
+/* { dg-do compile } */
+/* { dg-options "-Wcompare-distinct-pointer-types" } */
+
+typedef int __u32;
+
+struct xdp_md
+{
+ char *data;
+ char *data_meta;
+};
+
+int xdp_context (struct xdp_md *xdp)
+{
+ void *data = (void *)(long)xdp->data;
+ __u32 *metadata = (void *)(long)xdp->data_meta;
+ __u32 ret;
+
+ if (metadata + 1 > data) /* { dg-warning "comparison of distinct pointer types" } */
+ return 1;
+ if (metadata + 1 >= data) /* { dg-warning "comparison of distinct pointer types" } */
+ return 2;
+ if (metadata + 1 < data) /* { dg-warning "comparison of distinct pointer types" } */
+ return 3;
+ if (metadata + 1 <= data) /* { dg-warning "comparison of distinct pointer types" } */
+ return 4;
+ if (metadata + 1 == data) /* { dg-warning "comparison of distinct pointer types" } */
+ return 5;
+ if (metadata + 1 != data) /* { dg-warning "comparison of distinct pointer types" } */
+ return 5;
+
+ return 1;
+}
diff --git a/gcc/testsuite/gcc.c-torture/compile/pr106537-3.c b/gcc/testsuite/gcc.c-torture/compile/pr106537-3.c
new file mode 100644
index 000000000000..73c9b251824d
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/compile/pr106537-3.c
@@ -0,0 +1,32 @@
+/* { dg-do compile } */
+/* { dg-options "-O0 -Wno-compare-distinct-pointer-types" } */
+
+typedef int __u32;
+
+struct xdp_md
+{
+ char *data;
+ char *data_meta;
+};
+
+int xdp_context (struct xdp_md *xdp)
+{
+ void *data = (void *)(long)xdp->data;
+ __u32 *metadata = (void *)(long)xdp->data_meta;
+ __u32 ret;
+
+ if (metadata + 1 > data) /* There shouldn't be a warning here. */
+ return 1;
+ if (metadata + 1 >= data) /* There shouldn't be a warning here. */
+ return 2;
+ if (metadata + 1 < data) /* There shouldn't be a warning here. */
+ return 3;
+ if (metadata + 1 <= data) /* There shouldn't be a warning here. */
+ return 4;
+ if (metadata + 1 == data) /* There shouldn't be a warning here. */
+ return 5;
+ if (metadata + 1 != data) /* There shouldn't be a warning here. */
+ return 5;
+
+ return 1;
+}
--
GitLab