On Fri, May 29, 2020 at 01:26:32PM -0400, Jason Merrill via Gcc-patches wrote:
> This is a diagnostic quality regression, moving the error message away from
> the line where the actual problem is.
>
> Maybe use error_at (loc, ...)?
That works fine, bootstrapped/regtested on x86_64-linux and i686-linux, ok
for trunk?
2020-06-02 Jakub Jelinek <ja...@redhat.com>
PR c++/82304
PR c++/95307
* constexpr.c (cxx_eval_constant_expression): Diagnose CONVERT_EXPR
conversions from pointer types to arithmetic types here...
(cxx_eval_outermost_constant_expr): ... instead of here.
* g++.dg/template/pr79650.C: Expect different diagnostics and expect
it on all lines that do pointer to integer casts.
* g++.dg/cpp1y/constexpr-shift1.C: Expect different diagnostics.
* g++.dg/cpp1y/constexpr-82304.C: New test.
* g++.dg/cpp0x/constexpr-95307.C: New test.
--- gcc/cp/constexpr.c.jj 2020-05-29 23:49:25.479087388 +0200
+++ gcc/cp/constexpr.c 2020-06-01 12:53:30.348337388 +0200
@@ -6210,6 +6210,18 @@ cxx_eval_constant_expression (const cons
if (VOID_TYPE_P (type))
return void_node;
+ if (TREE_CODE (t) == CONVERT_EXPR
+ && ARITHMETIC_TYPE_P (type)
+ && INDIRECT_TYPE_P (TREE_TYPE (op)))
+ {
+ if (!ctx->quiet)
+ error_at (loc,
+ "conversion from pointer type %qT to arithmetic type "
+ "%qT in a constant expression", TREE_TYPE (op), type);
+ *non_constant_p = true;
+ return t;
+ }
+
if (TREE_CODE (op) == PTRMEM_CST && !TYPE_PTRMEM_P (type))
op = cplus_expand_constant (op);
@@ -6811,19 +6823,6 @@ cxx_eval_outermost_constant_expr (tree t
non_constant_p = true;
}
- /* Technically we should check this for all subexpressions, but that
- runs into problems with our internal representation of pointer
- subtraction and the 5.19 rules are still in flux. */
- if (CONVERT_EXPR_CODE_P (TREE_CODE (r))
- && ARITHMETIC_TYPE_P (TREE_TYPE (r))
- && TREE_CODE (TREE_OPERAND (r, 0)) == ADDR_EXPR)
- {
- if (!allow_non_constant)
- error ("conversion from pointer type %qT "
- "to arithmetic type %qT in a constant expression",
- TREE_TYPE (TREE_OPERAND (r, 0)), TREE_TYPE (r));
- non_constant_p = true;
- }
if (!non_constant_p && overflow_p)
non_constant_p = true;
--- gcc/testsuite/g++.dg/template/pr79650.C.jj 2020-05-29 23:49:19.040183088
+0200
+++ gcc/testsuite/g++.dg/template/pr79650.C 2020-06-01 12:53:30.348337388
+0200
@@ -11,10 +11,10 @@ foo ()
static int a, b;
lab1:
lab2:
- A<(intptr_t)&&lab1 - (__INTPTR_TYPE__)&&lab2> c; // { dg-error "not a
constant integer" }
- A<(intptr_t)&&lab1 - (__INTPTR_TYPE__)&&lab1> d;
- A<(intptr_t)&a - (intptr_t)&b> e; // { dg-error "is not a
constant expression" }
- A<(intptr_t)&a - (intptr_t)&a> f;
- A<(intptr_t)sizeof(a) + (intptr_t)&a> g; // { dg-error "not a
constant integer" }
+ A<(intptr_t)&&lab1 - (__INTPTR_TYPE__)&&lab2> c; // { dg-error
"conversion from pointer type" }
+ A<(intptr_t)&&lab1 - (__INTPTR_TYPE__)&&lab1> d; // { dg-error
"conversion from pointer type" }
+ A<(intptr_t)&a - (intptr_t)&b> e; // { dg-error
"conversion from pointer type" }
+ A<(intptr_t)&a - (intptr_t)&a> f; // { dg-error
"conversion from pointer type" }
+ A<(intptr_t)sizeof(a) + (intptr_t)&a> g; // { dg-error
"conversion from pointer type" }
A<(intptr_t)&a> h; // { dg-error
"conversion from pointer type" }
}
--- gcc/testsuite/g++.dg/cpp1y/constexpr-shift1.C.jj 2020-05-29
23:49:19.036183148 +0200
+++ gcc/testsuite/g++.dg/cpp1y/constexpr-shift1.C 2020-06-01
13:55:22.607594689 +0200
@@ -3,7 +3,7 @@
constexpr int p = 1;
constexpr __PTRDIFF_TYPE__ bar (int a)
{
- return ((__PTRDIFF_TYPE__) &p) << a; // { dg-error "is not a constant
expression" }
+ return ((__PTRDIFF_TYPE__) &p) << a; // { dg-error "conversion from pointer"
}
}
constexpr __PTRDIFF_TYPE__ r = bar (2); // { dg-message "in .constexpr.
expansion of" }
-constexpr __PTRDIFF_TYPE__ s = bar (0); // { dg-error "conversion from
pointer" }
+constexpr __PTRDIFF_TYPE__ s = bar (0);
--- gcc/testsuite/g++.dg/cpp1y/constexpr-82304.C.jj 2020-06-01
12:53:30.349337373 +0200
+++ gcc/testsuite/g++.dg/cpp1y/constexpr-82304.C 2020-06-01
13:03:40.668227604 +0200
@@ -0,0 +1,14 @@
+// PR c++/82304
+// { dg-do compile { target c++14 } }
+
+typedef __UINTPTR_TYPE__ uintptr_t;
+
+constexpr const char *
+foo (const char *p)
+{
+ auto l = reinterpret_cast<uintptr_t>(p); // { dg-error "conversion from
pointer" }
+ ++l;
+ return reinterpret_cast<const char *>(l);
+}
+
+constexpr auto s = foo ("Hello");
--- gcc/testsuite/g++.dg/cpp0x/constexpr-95307.C.jj 2020-06-01
12:53:30.349337373 +0200
+++ gcc/testsuite/g++.dg/cpp0x/constexpr-95307.C 2020-06-01
12:53:30.349337373 +0200
@@ -0,0 +1,5 @@
+// PR c++/95307
+// { dg-do compile { target c++11 } }
+
+int v;
+constexpr auto p{reinterpret_cast<__UINTPTR_TYPE__>(&v) - 1u}; // { dg-error
"conversion from pointer type" }
Jakub
