Hi!
The warning code uses %D to print the ARRAY_REF first operands.
That works in the most common case where those operands are decls, but
as can be seen on the following testcase, they can be other expressions
with array type.
Just changing %D to %E isn't enough, because then the diagnostics can
suggest something like
note: use '&(x) != 0 ? (int (*)[32])&a : (int (*)[32])&b[0] == &(y) != 0 ? (int
(*)[32])&a : (int (*)[32])&b[0]' to compare the addresses
which is a bad suggestion, the %E printing doesn't know that the
warning code will want to add & before it and [0] after it.
So, the following patch adds ()s around the operand as well, but does
that only for non-decls, for decls keeps it as &arr[0] like before.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk
and release branches?
2024-06-17 Jakub Jelinek <ja...@redhat.com>
PR c/115290
* c-warn.cc (do_warn_array_compare): Use %E rather than %D for
printing op0 and op1; if those operands aren't decls, also print
parens around them.
* c-c++-common/Warray-compare-3.c: New test.
--- gcc/c-family/c-warn.cc.jj 2024-06-04 13:19:03.371609456 +0200
+++ gcc/c-family/c-warn.cc 2024-06-17 15:07:09.005737065 +0200
@@ -3832,11 +3832,16 @@ do_warn_array_compare (location_t locati
/* 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);
+ "or %<&%s%E%s[0] %s &%s%E%s[0]%> to compare the addresses",
+ DECL_P (op0) ? "" : "(", op0, DECL_P (op0) ? "" : ")",
+ op_symbol_code (code),
+ DECL_P (op1) ? "" : "(", op1, DECL_P (op1) ? "" : ")");
else
- inform (location, "use %<&%D[0] %s &%D[0]%> to compare the addresses",
- op0, op_symbol_code (code), op1);
+ inform (location,
+ "use %<&%s%E%s[0] %s &%s%E%s[0]%> to compare the addresses",
+ DECL_P (op0) ? "" : "(", op0, DECL_P (op0) ? "" : ")",
+ op_symbol_code (code),
+ DECL_P (op1) ? "" : "(", op1, DECL_P (op1) ? "" : ")");
}
}
--- gcc/testsuite/c-c++-common/Warray-compare-3.c.jj 2024-06-17
15:13:57.098422635 +0200
+++ gcc/testsuite/c-c++-common/Warray-compare-3.c 2024-06-17
15:13:24.339849049 +0200
@@ -0,0 +1,13 @@
+/* PR c/115290 */
+/* { dg-do compile } */
+/* { dg-options "-Warray-compare" } */
+
+int a[32][32], b[32][32];
+
+int
+foo (int x, int y)
+{
+ return (x ? a : b) == (y ? a : b); /* { dg-warning "comparison between two
arrays" } */
+/* { dg-message "use '&\\\(\[^\n\r]*\\\)\\\[0\\\] ==
&\\\(\[^\n\r]*\\\)\\\[0\\\]' to compare the addresses" "" { target c } .-1 } */
+/* { dg-message "use unary '\\\+' which decays operands to pointers or
'&\\\(\[^\n\r]*\\\)\\\[0\\\] == &\\\(\[^\n\r]*\\\)\\\[0\\\]' to compare the
addresses" "" { target c++ } .-2 } */
+}
Jakub
