Thread: passing struct containing char string into a function

  1. #1
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    passing struct containing char string into a function

    I have a header file containing:
    Code:
    struct confTimer{
        char name[3];
        char direction[8];
        uint countValue;
    };
    
    
    uint run_timer(struct confTimer cT);
    I have a function file containing:
    Code:
    uint run_timer(struct confTimer cT){
        if (!strcmp(cT.name, "B0")) {
    I have main (separate file) containing:
    Code:
        struct confTimer radioT;
    
    
    
    
    	radioT.name[3] = "B0";
    	radioT.direction[8] = "up_down";
    	radioT.countValue = 4455;
            run_timer(radioT);
    I am never stepping into the function at the conditional if...What am I missing?
    Thanks

  2. #2
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    You can not assign c-string in C!
    You need to use strcpy or strncpy function to copy C-strings.

    I suggest reading the warning you get while compiling!

    Tim S.
    "...a computer is a stupid machine with the ability to do incredibly smart things, while computer programmers are smart people with the ability to do incredibly stupid things. They are,in short, a perfect match.." Bill Bryson

  3. #3
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    Code:
    radioT.name[3] = "B0";
    And, this is wrong even in C++!

    In C++, this should work.

    Code:
    radioT.name = "B0";
    Tim S.
    "...a computer is a stupid machine with the ability to do incredibly smart things, while computer programmers are smart people with the ability to do incredibly stupid things. They are,in short, a perfect match.." Bill Bryson

  4. #4
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    You should've got warnings with that code. Don't ignore warnings.
    You need to use strcpy to set the contents of a string.
    And you should probably pass the struct by pointer.
    Code:
    #include <stdio.h>
    #include <string.h>
     
    typedef unsigned int uint;
     
    struct confTimer{
        char name[3];
        char direction[8];
        uint countValue;
    };
     
    uint run_timer(struct confTimer *cT){
        if (!strcmp(cT->name, "B0")) {
            printf("%s, %d\n", cT->direction, cT->countValue);
        }
        return 0;
    }
     
    int main() {
        struct confTimer radioT;
        strcpy(radioT.name, "B0");
        strcpy(radioT.direction, "up_down");
        radioT.countValue = 4455;
        run_timer(&radioT);
        return 0;
    }
    Philosophy is a battle against the bewitchment of our intelligence by means of language. - Wittgenstein

  5. #5
    C++ Witch laserlight's Avatar
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    If you want to initialise, you can do so with an aggregate:
    Code:
    struct confTimer radioT = {"B0", "up_down", 4455};
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

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