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* [PATCH V4] Add warning options -W[no-]compare-distinct-pointer-types
@ 2023-08-17 14:05 Jose E. Marchesi
  2023-08-17 15:23 ` Joseph Myers
  2024-06-15  8:31 ` Gerald Pfeifer
  0 siblings, 2 replies; 7+ messages in thread
From: Jose E. Marchesi @ 2023-08-17 14:05 UTC (permalink / raw)
  To: gcc-patches; +Cc: joseph

[Changes from V3:
- Previous thread:
  https://gcc.gnu.org/pipermail/gcc-patches/2022-August/600625.html
- The tests have been augmented to check all six relational
  operators.  In particular it covers both code paths impacted
  by the patch: the equality/inequality and the relational ops.]

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 c7b567ba7ab..2242524cd3e 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 6f2fff51683..e6ddf37d412 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 3380ed8bd6f..28ee6fb62bb 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
+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 00000000000..3f3b06577d5
--- /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 00000000000..6876adf3aab
--- /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 00000000000..73c9b251824
--- /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;
+}
-- 
2.30.2


^ permalink raw reply	[flat|nested] 7+ messages in thread
end of thread, other threads:[~2024-06-17  9:12 UTC | newest]

Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2023-08-17 14:05 [PATCH V4] Add warning options -W[no-]compare-distinct-pointer-types Jose E. Marchesi
2023-08-17 15:23 ` Joseph Myers
2023-08-17 15:37   ` Jose E. Marchesi
2023-08-23 18:12     ` Marek Polacek
2023-08-24 15:18       ` Jose E. Marchesi
2024-06-15  8:31 ` Gerald Pfeifer
2024-06-17  9:11   ` Jose E. Marchesi

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