Structs and Malloc

Comments

• AsmGuru62

  May 2010

  [color=Blue]I can see two things:
  
  1. The IF() statement with allocation has misplaced bracket.
  2. Incorrect way of assigning one string to another string.
  
  In general strcpy() is the only way.
  
  Also, I do not see how loadData() function is called - with which parameters?
  [/color]
  : Hiya, I've been trying to allocate memory and put a single letter in
  : an array within a struct that I know can actually fit it in. At the
  : end of the day it just gives me a Segmentation Error and I'm back to
  : wondering what I'm doing wrong.
  :
  : Here's all the code.
  :
  : [code]:
  : int loadData(PMSType* pms, char* programFile, char* courseFile)
  : {
  : char input[PROG_ID_LEN + 1] = "P0001";
  : ProgramType *prog;
  : printf("Debug: Attempting to allocate memory");
  : if((prog =(ProgramType *) malloc(sizeof(ProgramType))[color=Red])[/color] == NULL)
  : printf("Error: Could not allocate memory");
  : else{
  : printf("Debug: Attempting to put p in progID[0]");
  : prog->progID[0] = 'p';
  : strcpy(prog->progID, "p");
  : [color=Red]/*prog->progID = input; - not a proper way!*/[/color]
  : strcpy(prog->progID, input);
  : }
  :
  : }
  :
  :
  : typedef struct program
  : {
  : char progID[PROG_ID_LEN + 1]; /* Unique ID for a program */
  : char progTitle[MAX_TITLE_LEN + 1];
  : char progMajor[MAX_TITLE_LEN + 1];
  : char progCode[PROG_CODE_LEN + 1];
  : float progDuration;
  : char progType[PROG_TYPE_LEN]; /* Undergrade(UG) or Postgrad (PG) */
  : char progMode[MODE_LEN]; /* Full-time (FT) or Part-time (PT) */
  : char progDescription[MAX_DESC_LEN];
  : char majorDescription[MAX_DESC_LEN];
  : ProgramTypePtr nextProgram;
  : CourseTypePtr headCourse;
  : unsigned numCourses;
  : } ProgramType;
  :
  : typedef struct pms
  : {
  : ProgramTypePtr headProgram;
  : unsigned numPrograms;
  : } PMSType;
  :
  : [/code]:
  :
  : Also, it has told me that I have to initialise the system to a safe
  : empty place... and I'm wondering if this is what I am supposed to
  : put.
  :
  : [code]:
  : int systemInit(PMSType* pms)
  : {
  : pms = (PMSType *) malloc(sizeof(*pms));
  : if(pms == NULL)
  : printf("Error: Couldn't Allocate
  ");
  : else{
  : printf("Successfully allocated
  ");
  : }
  : }
  : [/code]:
  
• Aphillios

  May 2010

  LoadData() is called in the main function with pms, and two arguments from the command line, I felt that it wasn't necessary to add that as I'm just wondering whether I am doing anything wrong with malloc and adding to an array of chars in a struct.
  
  Everytime I try that strcpy(prog->progID, input); or indeed strcpy(prog->progID, "p"); it gives me an error of a mismatched type between Char[6] and Char * or Char (*) [6] and I have no idea what to do about that.
• AsmGuru62

  May 2010

  [color=Blue]Your compiler is at fault here. Which compiler is it?
  I just tried it with Visual C++ 2005 and it all compiles fine.
  I adjusted the code, so it will compile as pure C code:[/color]
  [code]
  // j001.cpp : Defines the entry point for the console application.
  //
  
  #include
  #include
  #include
  
  #define PROG_ID_LEN 32
  #define MAX_TITLE_LEN 32
  #define PROG_CODE_LEN 32
  #define PROG_TYPE_LEN 32
  #define MODE_LEN 32
  #define MAX_DESC_LEN 32
  
  typedef struct tag_ProgramType
  {
  char progID[PROG_ID_LEN + 1]; /* Unique ID for a program */
  char progTitle[MAX_TITLE_LEN + 1];
  char progMajor[MAX_TITLE_LEN + 1];
  char progCode[PROG_CODE_LEN + 1];
  float progDuration;
  char progType[PROG_TYPE_LEN]; /* Undergrade(UG) or Postgrad (PG) */
  char progMode[MODE_LEN]; /* Full-time (FT) or Part-time (PT) */
  char progDescription[MAX_DESC_LEN];
  char majorDescription[MAX_DESC_LEN];
  struct tag_ProgramType* nextProgram;
  //CourseType* headCourse;
  unsigned numCourses;
  } ProgramType;
  
  typedef struct pms
  {
  ProgramType* headProgram;
  unsigned numPrograms;
  } PMSType;
  
  int loadData(PMSType* pms, char* programFile, char* courseFile)
  {
  char input[PROG_ID_LEN + 1] = "P0001";
  ProgramType *prog;
  printf("Debug: Attempting to allocate memory");
  if((prog =(ProgramType *) malloc(sizeof(ProgramType))) == NULL)
  printf("Error: Could not allocate memory");
  else{
  printf("Debug: Attempting to put p in progID[0]");
  prog->progID[0] = 'p';
  strcpy(prog->progID, "p");
  strcpy(prog->progID, input);
  }
  return 0;
  }
  
  int main(int argc, char* argv[])
  {
  return 0;
  }
  [/code]
  [color=Blue]There was a few warnings, but they were not connected to strcpy().[/color]