While 3.4 made substantial improvements on handling of template parameters,
there are still some incorrect compiler errors that are triggered with a
combination of complexity in the template arguments and levels of templates.
In the testcase below, gcc will error out with:
t.cxx: In function void foo_function(ch_t, ch_t, ch_t*):
t.cxx:20: error: (((int)false) + 7) is not a valid template argument for
type int because it is a non-constant expression
t.cxx:20: error: no match for operator+ in A + B
The error goes away if the function foo_function (that calls the
my_int::operator +) is un-templatized. Note that the template parameter for
foo_function is not even used anywhere in the function so it should have no
impact. Simplifying the expression for the template parameters on the return
type of my_int::operator + also makes the error go away.
#define MAX(a,b) ((a) > (b) ? (a) : (b))
template<int W, bool S>
class mc_int {
public:
int d;
mc_int() { d = 0; }
mc_int(int x) { d = x; }
mc_int(const mc_int &x) { d = x.d; }
template<int W2, bool S2>
mc_int<MAX(W+(S2&&!S),W2+(S&&!S2))+1, (S||S2)> operator +(const mc_int<W2,S2>
& x) const {
return 0;
}
};
typedef mc_int<6,false> ch_t;
template <int footemplate>
void foo_function(ch_t A, ch_t B, ch_t *C) {
A + B;
}
int main() {
ch_t fooA, fooB, fooC, fooD, fooE;
fooA= (ch_t) 5;
fooB= (ch_t) 15;
ch_t CC;
foo_function<0>(fooA, fooB, &CC);
}
--
Summary: compilation error when template parameters have certain
complexity
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: critical
Priority: P2
Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: andres_takach at mentor dot com
CC: gcc-bugs at gcc dot gnu dot org
GCC build triplet: gcc version 4.0.1
GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23789
