https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68699
Bug ID: 68699
Summary: Wrong location_t due to template instance
canonicalization when setting location_t values on
expressions
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: dmalcolm at gcc dot gnu.org
Target Milestone: ---
As discussed in the thread starting at
https://gcc.gnu.org/ml/gcc-patches/2015-12/msg00449.html
Testcase g++.dg/template/ref3.C:
1 // PR c++/28341
2
3 template<const int&> struct A {};
4
5 template<typename T> struct B
6 {
7 A<(T)0> b; // { dg-error "constant|not a valid" }
8 A<T(0)> a; // { dg-error "constant|not a valid" }
9 };
10
11 B<const int&> b;
With c++98, with trunk (e.g. r231208), we get this output
g++.dg/template/ref3.C: In instantiation of 'struct B<const int&>':
g++.dg/template/ref3.C:11:15: required from here
g++.dg/template/ref3.C:7:11: error: a cast to a type other than an integral or
enumeration type cannot appear in a constant-expression
g++.dg/template/ref3.C:8:11: error: a cast to a type other than an integral or
enumeration type cannot appear in a constant-expression
(locations 7:11 and 8:11 are at the closing semicolon for fields b and a)
Upon updating the C++ FE to set up location_t values for expressions,
in particular the bogus cast expressions (T)0 and T(0):
A<(T)0> b;
^~~~
and:
A<T(0)> a;
^~~~
both instantiations are reported at line 7, rather than at lines 7 and 8:
g++.dg/template/ref3.C:7:5: error: a cast to a type other than an integral or
enumeration type cannot appear in a constant-expression
g++.dg/template/ref3.C:7:5: error: a cast to a type other than an integral or
enumeration type cannot appear in a constant-expression
This is because both instantiations are using a single RECORD_TYPE
for the type A<(T)(0)>. We get a hit the 2nd time through this code
in pt.c:
8282 entry = type_specializations->find_with_hash (&elt, hash);
Hence when issuing both errors it uses the TREE_VEC of args for the
first one, rather than the most pertinent location.
