On Fri, Oct 01, 2021 at 11:15:45PM +0200, Jakub Jelinek wrote:
> On Fri, Oct 01, 2021 at 04:11:08PM -0400, Marek Polacek via Gcc-patches wrote:
> > + auto_diagnostic_group d;
> > + if (warning_at (location, OPT_Warray_compare,
> > + "comparison between two arrays%s",
> > + (c_dialect_cxx () && cxx_dialect >= cxx20)
> > + ? " is deprecated in C++20" : ""))
>
> Not a review, just a comment.
> The above is impossible to translate, translators would translate the
> first half and the second one would be in English; but even translating
> the second part too would mean one can't reword it in some other language
> in different word order.
>
> You can e.g. use
> if (warning_at (location, OPT_Warray_compare,
> (c_dialect_cxx () && cxx_dialect >= cxx20)
> ? G_("comparison between two arrays is deprecated in C++20")
> : G_("comparison between two arrays")))
> instead.
Thanks, fixed:
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
-- >8 --
This patch addresses one of my leftovers from GCC 11. C++20 introduced
[depr.array.comp]: "Equality and relational comparisons between two operands
of array type are deprecated." so this patch adds -Warray-compare. Since the
code in question is dubious (the comparison doesn't actually compare the array
elements), I've added this warning for C too, and enabled it in all C++ modes.
PR c++/97573
gcc/c-family/ChangeLog:
* c-common.h (do_warn_array_compare): Declare.
* c-warn.c (do_warn_array_compare): New.
* c.opt (Warray-compare): New option.
gcc/c/ChangeLog:
* c-typeck.c (parser_build_binary_op): Call do_warn_array_compare.
gcc/cp/ChangeLog:
* typeck.c (cp_build_binary_op): Call do_warn_array_compare.
gcc/ChangeLog:
* doc/invoke.texi: Document -Warray-compare.
gcc/testsuite/ChangeLog:
* c-c++-common/Warray-compare-1.c: New test.
* c-c++-common/Warray-compare-2.c: New test.
---
gcc/c-family/c-common.h | 1 +
gcc/c-family/c-warn.c | 32 ++
gcc/c-family/c.opt| 4 ++
gcc/c/c-typeck.c | 9 +++-
gcc/cp/typeck.c | 13 ++
gcc/doc/invoke.texi | 20 -
gcc/testsuite/c-c++-common/Warray-compare-1.c | 44 +++
gcc/testsuite/c-c++-common/Warray-compare-2.c | 44 +++
8 files changed, 164 insertions(+), 3 deletions(-)
create mode 100644 gcc/testsuite/c-c++-common/Warray-compare-1.c
create mode 100644 gcc/testsuite/c-c++-common/Warray-compare-2.c
diff --git a/gcc/c-family/c-common.h b/gcc/c-family/c-common.h
index 849cefab882..078730f1e64 100644
--- a/gcc/c-family/c-common.h
+++ b/gcc/c-family/c-common.h
@@ -1421,6 +1421,7 @@ extern bool warn_for_restrict (unsigned, tree *,
unsigned);
extern void warn_for_address_or_pointer_of_packed_member (tree, tree);
extern void warn_parm_array_mismatch (location_t, tree, tree);
extern void maybe_warn_sizeof_array_div (location_t, tree, tree, tree, tree);
+extern void do_warn_array_compare (location_t, tree_code, tree, tree);
/* Places where an lvalue, or modifiable lvalue, may be required.
Used to select diagnostic messages in lvalue_error and
diff --git a/gcc/c-family/c-warn.c b/gcc/c-family/c-warn.c
index 84ad6633c96..99cde4a2a59 100644
--- a/gcc/c-family/c-warn.c
+++ b/gcc/c-family/c-warn.c
@@ -3726,3 +3726,35 @@ maybe_warn_sizeof_array_div (location_t loc, tree arr,
tree arr_type,
}
}
}
+
+/* Warn about C++20 [depr.array.comp] array comparisons: "Equality
+ and relational comparisons between two operands of array type are
+ deprecated." We also warn in C and earlier C++ standards. CODE is
+ the code for this comparison, OP0 and OP1 are the operands. */
+
+void
+do_warn_array_compare (location_t location, tree_code code, tree op0, tree op1)
+{
+ STRIP_NOPS (op0);
+ STRIP_NOPS (op1);
+ if (TREE_CODE (op0) == ADDR_EXPR)
+op0 = TREE_OPERAND (op0, 0);
+ if (TREE_CODE (op1) == ADDR_EXPR)
+op1 = TREE_OPERAND (op1, 0);
+
+ auto_diagnostic_group d;
+ if (warning_at (location, OPT_Warray_compare,
+ (c_dialect_cxx () && cxx_dialect >= cxx20)
+ ? G_("comparison between two arrays is deprecated in C++20")
+ : G_("comparison between two arrays")))
+{
+ /* C doesn't allow +arr. */
+ if (c_dialect_cxx ())
+ inform (location, "use unary %<+%> which decays operands to pointers "
+ "or %<&%D[0] %s &%D[0]%> to compare the addresses",
+ op0, op_symbol_code (code), op1);
+ else
+ inform (location, "use %<&%D[0] %s &%D[0]%> to compare the addresses",
+ op0, op_symbol_code (code), op1);
+}
+}
diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index 9c151d19870..06457ac739e 100644
---
