c: declare static array in header file

[gmauger]

Hi All,

I'd like to declare a static array in a header file. Is this possible?

I assume there is a fairly simple solution to this, but I have not been able to find documentation on the correct syntax for this.

Just to be abundantly clear, I'd like to do the equivalent of:
int array[4] = {1,2,3,4};

in a header file.

Can someone tell me what the correct syntax is?

Thanks,
Guillaume

[Tom Gunn]

int array[4] = {1,2,3,4}; will work, but putting objects in headers is generally a bad idea because it is easy to accidentally define the object multiple times just by including the header more than once. Inclusion guards are only a partial fix for that problem.

Can you be specific about how the code you have tried does not work?

[gmauger]

int array[4] = {1,2,3,4}; will work, but putting objects in headers is generally a bad idea because it is easy to accidentally define the object multiple times just by including the header more than once. Inclusion guards are only a partial fix for that problem.

Can you be specific about how the code you have tried does not work?

Yes, sorry for the ambiguity. I have multiple .c scripts that refer to the same header file, as follows: #include "./my_header_file.h" Inside "my_header_file.h" I define a bunch of constants/macros that each program refers to, such as:

#define LEAPYEAR(year) ((year %4 == 0) && (((year % 100 == 0) && (year % 400 != 0)) == 0))
#define NORTH 53.125
#define SOUTH 41
#define EAST -109.75
#define WEST -125
#define NODATA -9999
#define NAMESFILEPATH "/raid/gmauger/flux_names"

I'd like to add a few arrays, e.g. something looking like: #define myARRAY[4] {1,2,3,4} ... I'm not clear on your answer above, esp regarding multiple definitions of the data... this may not be an issue because the programs I'm writing are really simple -- they are all just simple scripts that either summarize or manipulate data from a large batch of output files.

thanks again,
Guillaume

[Tom Gunn]

So what is the problem?

[gmauger]

So what is the problem?

The problem is that my compiler balks at the syntax I'm using to declare an array in the header file, and I can't find any documentation on what syntax to use, or even if it's possible to declare arrays (int or floating point) in a header file.

I'm fairly new to C, so if it seems like I'm not understanding something critical -- by all means, enlighten me.

[Tom Gunn]

It is impossible to help you without seeing the code that your compiler balks at and the errors that are thrown. Please post all of your code, or a small self-contained subset that has the error, and post all of the errors you get.

[gmauger]

It is impossible to help you without seeing the code that your compiler balks at and the errors that are thrown. Please post all of your code, or a small self-contained subset that has the error, and post all of the errors you get.

Got it. Sorry. Here is the header file (entitled "VIC_2860.h"):

#define NUMMONTHS 12
#define LEAPYEAR(year) ((year %4 == 0) && (((year % 100 == 0) && (year % 400 != 0)) == 0))

#define NORTH 53.125
#define SOUTH 41
#define EAST -109.75
#define WEST -125
#define LLINC .0625

#define NGRIDCELLS 24108
#define NLAT 195
#define NLON 245
#define NODATA -9999

#define NAMESFILEPATH "/raid/gmauger/data_processing/hb2860/VIC_SUMM/flux_names"
#define FLUXFLLIST "/raid/gmauger/data_processing/hb2860/VIC_SUMM/fluxfilelist_arc_pnw"
#define LATLONLIST "/raid/gmauger/data_processing/hb2860/VIC_SUMM/latlonlist_arc_pnw"

#define N_GLAC=22;
#define latGLAC[22] = {43.96875, 45.34375, 45.34375, 46.15625, 46.21875, 46.28125, 46.78125, 46.84375, 46.84375, 46.84375, 46.90625, 47.46875, 47.53125, 47.78125, 47.78125, 48.03125, 48.03125, 48.59375, 48.78125, 48.78125, 48.96875, 51.46875};
#define lonGLAC[22] = {-110.84375, -121.65625, -121.71875, -121.46875, -121.53125, -121.84375, -121.71875, -121.65625, -121.71875, -121.78125, -121.78125, -120.84375, -121.21875, -123.65625, -123.71875, -121.09375, -121.15625, -113.71875, -121.34375, -121.84375, -114.21875, -117.78125};

#define GRIDHEADER "ncols\t245\nnrows\t195\nxllcorner\t-125\nyllcorner\t41\ncellsize\t0.0625\nNODATA_value\t-9999\n"

And here is the .c script that calls it:

#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include "./VIC_2860.h"

int main(int argc, char* argv[]) {

    char inpathstr[150], outpathstr[150];
    FILE *fileIN, *fileOUT;
    float latlondat[NGRIDCELLS][3], outROW[NLON];
    float fLAT, fLON;
    int q, i, rmGLAC;

    // Check arguments: 
    if (argc != 4) {
                puts("Wrong command line arguments: enter <summary file name> <gridinfo file name> <rmGLAC>\n");
                exit (1);
    }

    // READ ARGUMENT STRINGS:
    sscanf(argv[1],"%s",inpathstr);
    sscanf(argv[2],"%s",outpathstr);
    sscanf(argv[3],"%d",&rmGLAC);
    if ( rmGLAC == 1 ) { printf("    ***Removing glaciating cells:\n"); }

    // READ IN INPUT (MEAN-OF-SUMMARY) FILE:
    if ((fileIN = fopen(inpathstr, "r")) == NULL) {
                printf("error:  cannot open %s\n", inpathstr);
                exit(1);
    }
    q=0;
    while(fscanf(fileIN,"%f %f %f",&latlondat[q][0],&latlondat[q][1],&latlondat[q][2]) != EOF){
      //printf("%f %f %f\n",latlondat[q][0],latlondat[q][1],latlondat[q][2]);
      q++;
    }
    fclose(fileIN);
    //printf("    NGRIDCELLS = %d \n",NGRIDCELLS);
    //printf("    number of rows in input file: %d \n",q);

    // OPEN OUTPUT FILE:
    printf("    saving: %s\n",outpathstr);
    if ((fileOUT = fopen(outpathstr, "w")) == NULL) {
                printf("Can't open output file %s", outpathstr);
                exit(1);
     }
    fputs(GRIDHEADER, fileOUT);   // ADD HEADER AS FIRST LINE

    // WRITE TO GRID FILE, ONE LAT ROW AT A TIME
    for ( fLAT = NORTH+LLINC/2; fLAT >= SOUTH; (fLAT -= LLINC) ) {
        for ( fLON = WEST+LLINC/2; fLON <= EAST+LLINC/2; (fLON += LLINC) ) {

            // find 1D position of grid point
            q=0;
            while ( ( latlondat[q][0] != fLAT || latlondat[q][1] != fLON ) && q < NGRIDCELLS ) {
                q++;
            }

            // if exists, print value, else, pring NODATA
            if ( q == NGRIDCELLS && ( latlondat[q][0] != SOUTH || latlondat[q][1] != EAST ) ) {
                fprintf(fileOUT, "%d ",NODATA);
            }
            else {
                // Check for glaciated cells
                i=0;
                while ( ( fLAT != latGLAC[i] || fLON != lonGLAC[i] ) && i < N_GLAC ) {
                    i++;
                }

                // only print data if not glaciated or if not removing glaciated cells
                if ( rmGLAC == 1 && i != N_GLAC ) {
                    fprintf(fileOUT, "%d ",NODATA);
                    //printf("fluxes_%f_%f\n",latGLAC[i],lonGLAC[i]);
                }
                else {
                    fprintf(fileOUT, "%.1f ",latlondat[q][2]);
                }
            }
        }
        // print new line
        fprintf(fileOUT, "\n");

        // sanity check:
        //printf("LAT: %f, LON RANGE: %f - %f \n",fLAT,WEST+LLINC/2,fLON);

    }
    fclose(fileOUT);
}

And here are the errors I get on compiling it:

[guillaume: ~]$ gcc -o summ2grdasc summ2grdasc.c
In file included from summ2grdasc.c:13:
./VIC_2860.h:21:15: warning: ISO C requires whitespace after the macro name
./VIC_2860.h:22:16: warning: ISO C requires whitespace after the macro name
./VIC_2860.h:23:16: warning: ISO C requires whitespace after the macro name
summ2grdasc.c: In function `main':
summ2grdasc.c:81: error: syntax error before '[' token
summ2grdasc.c:81: error: syntax error before '=' token
summ2grdasc.c:86: error: syntax error before '=' token
summ2grdasc.c: At top level:
summ2grdasc.c:95: error: syntax error before '}' token
summ2grdasc.c:97: error: syntax error before string constant
summ2grdasc.c:97: error: conflicting types for 'fprintf'
summ2grdasc.c:97: note: a parameter list with an ellipsis can't match an empty parameter name list declaration
summ2grdasc.c:97: error: conflicting types for 'fprintf'
summ2grdasc.c:97: note: a parameter list with an ellipsis can't match an empty parameter name list declaration
summ2grdasc.c:97: warning: data definition has no type or storage class
summ2grdasc.c:103: warning: parameter names (without types) in function declaration
summ2grdasc.c:103: warning: data definition has no type or storage class
summ2grdasc.c:104: error: syntax error before '}' token

If I comment out the array declarations in the header file, and put them instead directly into the .c script, then the code compiles and runs w/o any problems.

[Tom Gunn]

Replace this part of your header:

#define N_GLAC=22;
#define latGLAC[22] = {43.96875, 45.34375, 45.34375, 46.15625, 46.21875, 46.28125, 46.78125, 46.84375, 46.84375, 46.84375, 46.90625, 47.46875, 47.53125, 47.78125, 47.78125, 48.03125, 48.03125, 48.59375, 48.78125, 48.78125, 48.96875, 51.46875};
#define lonGLAC[22] = {-110.84375, -121.65625, -121.71875, -121.46875, -121.53125, -121.84375, -121.71875, -121.65625, -121.71875, -121.78125, -121.78125, -120.84375, -121.21875, -123.65625, -123.71875, -121.09375, -121.15625, -113.71875, -121.34375, -121.84375, -114.21875, -117.78125};

With this:

#define N_GLAC 22
double latGLAC[22] = {43.96875, 45.34375, 45.34375, 46.15625, 46.21875, 46.28125, 46.78125, 46.84375, 46.84375, 46.84375, 46.90625, 47.46875, 47.53125, 47.78125, 47.78125, 48.03125, 48.03125, 48.59375, 48.78125, 48.78125, 48.96875, 51.46875};
double lonGLAC[22] = {-110.84375, -121.65625, -121.71875, -121.46875, -121.53125, -121.84375, -121.71875, -121.65625, -121.71875, -121.78125, -121.78125, -120.84375, -121.21875, -123.65625, -123.71875, -121.09375, -121.15625, -113.71875, -121.34375, -121.84375, -114.21875, -117.78125};

There were two problems. First is you were defining N_GLAC the wrong way for a macro. Macros do not use the = sign to assign a value, and they do not end with a semicolon. Second, you were trying to define arrays with macro syntax. A header is nothing special when it comes to defining objects. You do it the same way as any global variable.

[gmauger]

It works! Thanks!