Thread: Doubt regarding C structures and arrays. Quick suggestions please

  1. 05-09-2009 #1
    cyrux
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    Doubt regarding C structures and arrays. Quick suggestions please

    I have a doubt regarding C pointers, structures and arrays.

    Code:
    I have a structure
typedef nx_struct DataMsg {
nx_uint16_t destID;
nx_uint16_t sourceID;
nx_uint16_t valueReported[100];
} DataMsg;
    I have a variable named a .
    Code:
    a[100] ={100 values}
    I have a pointer created for a datapkt
    Code:
    DataMsg* datapkt = (DataMsg*) (call RadioPacket.getPayload(&radiopkt, NULL));
    i need to set the array of the structure to the value of a

    isnt this right
    Code:
    datapkt->valueReported = a; ?
    Gives me an error saying , invalid lvalue in assignment

    The data types mentioned above are similar to regular int

    An explanation would be good as well.
  2. 05-09-2009 #2
    laserlight
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    You cannot assign to an array, so you should use say, memcpy() instead.
    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
  3. 05-09-2009 #3
    cyrux
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    isnt there a concept of shallow copy in C?
  4. 05-09-2009 #4
    laserlight
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    Quote Originally Posted by cyrux
    isnt there a concept of shallow copy in C?
    If you are copying a pointer without copying what it points to, yes. But here you have an array, not a pointer.
    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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