Core dump with stlport4 and string pointers

Question

Hello,
I am porting from SGI Irix to Sun Solaris, using OS 8 and Sun Studio 8. The program we are porting is very very large. We've compiled all code, but now are getting core dumps on several of the executables. We have traced one of the core dumps to a function that deals with string manipulation/string pointers. We wrote a very simple test program that re-produces the problem.
#include <string>
#include <iostream>
void test(char* m)
std::cout << m << " in test before";
m[0] = 'z';
std::cout << m << " in test after";
void main(void)
char* temp = new char[10];
temp = "abcd";
std::cout << temp << " before test";
test(temp);
std::cout << temp << " after test";
We get the following output:
abcd before test
abcd in test before
Segmentation fault (core dumped)
The code compiles and runs fine on the SGI Irix system. What am I doing wrong?
Thanks,
Bob

Answer 1

1) The signature of "main" is wrong. It must be 'int
main(int, char **)'Not quite. The signatures
int main()
int main(void)
are also allowed. (C++ standard, section 3.6.1 Main function)
A "void" return type on main is not standard, but Sun C++ allows it with a warning. Such a version of main does not return a predictable value to the program that invoked it (usually the shell).
It seems as if the intent of the program is to
allocate a new string with the contents "abcd".
Instead, you allocate a buffer, and then overwrite the
pointer to that buffer with a pointer to a string
constant, to which you then attempt to write.Right. By default, the C++ compiler allocates string literals to read-only memory, to catch mistakes like this. The compiler has an option to store literal strings in read-write memory, but we recommend against using the option, since you should not ever want to modify a literal string.
I am curious why the compiler doesn't complain about
the assignment in main - to my eyes it looks like it
should be complaining that you are assigning a const
char * to a char *The compiler emits a warning about the assignment.
Such code is allowed but deprecated in the C++ standard, because of the deprecated conversion of "array of const char" to char* (section 4.2 Array-to-pointer conversion).