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Date: Fri, 08 Aug 2008 06:55:00 -0000
From: "Rohit Arul Raj" <rohitarulraj@gmail.com>
To: gcc-help <gcc-help@gcc.gnu.org>
Subject: odd behavior with Character Arrays
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Hi All,

Compiler Version: gcc 4.1.2 and gcc 3.4.6

Test Case:

unsigned int g = 0;
unsigned int slen(const char* c)
{
        int l = 0;
        while(*c != '\0') {
                ++l;
                ++c;
        }
        return l;
}

int main()
{
        unsigned int t;
        unsigned char n[] = {'a', 'b', 'c', 'd'};
        t = slen(n);
        g = slen(n);

        printf("\n t = %d, g1 = %d\n", t, g1);
        return 0;
}

I have a test case given above which is used to compute the string
length of the character array. In the test case, both 't' and 'g' call
the same function to compute the string length. But both these values
are different and they are wrong also.

With GCC 4.1.2,  t = 7, g = 5
With GCC 3.4.6,  t = 15, g = 5

This happens only when i don't provide the size of the array 'n'. If
size of the array is given "unsigned char n[15] = {'a', 'b', 'c',
'd'};" then the values are proper
t = 4 and g = 4.

1. Is this the expected behavior with GCC?
2. Can i get more details as to why if the size of the array is not
provided the compiler does not insert an string terminator at the end
of the array.
    This happens with both character as well as integer arrays.

Regards,
Rohit