C言語のコンパイルが上手くいきません

c
1#include <stdio.h>
2#include <stdlib.h>
3#include <string.h>
4#include <math.h>
5
6
7/*---------------------------*/
8/*   Conventional Routines   */
9/*---------------------------*/
10
11#define MxGEN   9
12#define RAD     (180./3.14159265359)
13#define MxMOD   19
14#define MxELM   ((MxMOD+1)*(MxMOD+1)-1)
15#define MxCOL   50
16#define LLINE   (MxCOL*9 + 10)
17
18void gigrf(int gen, double year)
19{   int maxod, i, n, m, l, k, ncol, nlin;
20    double y1, y2, yr1, yr2, dy;
21    double tzero, dmy[3], cb[MxELM], cv[MxELM];
22    char path[]="/home/SHARE/data/IGRFCOEF/igrf00.coef";
23    char file[]="/home/SHARE/data/IGRFCOEF/igrf00.coef";
24    char *pstr, *line, buf[LLINE];
25    FILE *fp;
26    if ((gen<1) || (MxGEN<gen))
27        { fprintf(stderr, "gigrf: unknown  NGEN = %d\n", gen); exit(1); }
28    strcpy(file, path);
29    if ((pstr=strstr(file,"00")) == NULL)
30        { fprintf(stderr, "gigrf: filename invalid\n"); exit(1); }
31    sprintf(buf, "%02d", gen); strncpy(pstr, buf, 2);
32    if ((fp=fopen(file,"r")) == NULL)
33        { fprintf(stderr, "gigrf: file not found\n"); exit(1); }
34    if (fgets(buf,LLINE,fp) == NULL)
35        { fprintf(stderr, "gigrf: file empty\n"); exit(1); }
36    if (sscanf(buf,"%d%d%lf%lf",&maxod,&ncol,&y1,&y2) != 4)
37        { fprintf(stderr, "gigrf: Line-1 format error\n"); exit(1); }
38    if ((maxod<8) || (maxod>MxMOD) || (ncol<2) || (ncol>MxCOL))
39        { fprintf(stderr, "gigrf: Line-1 invalid\n"); exit(1); }
40    nlin = (maxod+1)*(maxod+1) - 1;
41    if ((year<y1) || (year>y2))
42        fprintf(stderr, "gigrf: IGRF-%02d not defined for %9.3lf\n", gen,year);
43    if (fgets(buf,LLINE,fp) == NULL)
44        { fprintf(stderr, "gigrf: EOF before Line-2\n"); exit(1); }
45    line = &buf[1];
46    if (sscanf(line,"%*c%*d%*d%lf%n",&yr2,&n) == EOF)
47        { fprintf(stderr, "gigrf: Line-2 invalid\n"); exit(1); }
48    for (l=2; l<ncol; l++) {
49        line += n; yr1 = yr2;
50        if (sscanf(line,"%lf%n",&yr2,&n) == EOF)
51            { fprintf(stderr, "gigrf: Line-2 short\n"); exit(1); }
52        if (year < yr2) break;
53    }
54    for (i=0; i<nlin; i++) {
55        if (fgets(buf,LLINE,fp) == NULL)
56            { fprintf(stderr, "gigrf: EOF before Line-%d\n", i+3); exit(1); }
57        line = &buf[0];
58        if (sscanf(line,"%*c%*d%*d%n",&n) == EOF)
59            { fprintf(stderr, "gigrf: Line-%d invalid\n", i+3); exit(1); }
60        for (m=2; m<l; m++) {
61            line += n;
62            if (sscanf(line,"%*lf%n",&n) == EOF)
63                { fprintf(stderr, "gigrf: Line-%d short\n", i+3); exit(1); }
64        }
65        line += n;
66        if (sscanf(line,"%lf%lf",&cb[i],&cv[i]) != 2)
67            { fprintf(stderr, "gigrf: Line-%d short\n", i+3); exit(1); }
68    }
69    if (l == ncol) tzero = yr2;
70    else {
71        tzero = yr1; yr2 -= yr1;
72        for (i=0; i<nlin; i++) cv[i] = (cv[i]-cb[i])/yr2;
73    }
74    k = 0;
75    for (i=0,n=1; n<=maxod; n++) {
76        vgh[0][n]=cb[i]; vght[0][n]=cv[i]; i++;
77        if ((cb[i]!=0.) || (cv[i]!=0.)) k = n;
78        for (m=1; m<=n; m++) {
79            vgh[m][n]=cb[i]; vght[m][n]=cv[i]; i++;
80            if ((cb[i]!=0.) || (cv[i]!=0.)) k = n;
81            vgh[n][m-1]=cb[i]; vght[n][m-1]=cv[i]; i++;
82            if ((cb[i]!=0.) || (cv[i]!=0.)) k = n;
83        }
84    }
85    maxod = k;
86    field(6378.16, 298.25, 6371.2, maxod);
87    tcoef(vgh, vght, tzero, 0, dmy); tyear(year);
88}
89
90void igrfc(double fido, double fkeido, double hght, double *tf)
91{   double fx, fy, fz;
92    mfldg(fido, fkeido, hght/1000., &fx, &fy, &fz, tf);
93}
94
95void igrfm(double fm[6])
96{   double gx, gy, gz, h, dip, dec;
97    gcomp(&gx, &gy, &gz);
98    h=sqrt(gx*gx+gy*gy); dip=atan2(gz,h); dec=atan2(gy,gx);
99    fm[0]=gx; fm[1]=gy; fm[2]=gz; fm[3]=h; fm[4]=dip*RAD; fm[5]=dec*RAD;
100}
101
102
103void sigrf(double year)
104{   int maxod, i, n, m, l;
105    double tzero, dmy[3];
106    l=(int)(year-1970.)/5; if (l < 0) l=0; else if (l >= 7) l=6;
107    if (l < 2) maxod=8; else maxod=10;
108    tzero=(double)(l*5 + 1970); if (l==0) tzero=1965.;
109    if ((year<1955.) || (year>2005.))
110        fprintf(stderr, "sigrf: IGRF not available for %8.3lf\n", year);
111    for (i=0,n=1; n<=maxod; n++) {
112        vgh[0][n]=rf[l][i];
113        if (n<=8) vght[0][n]=sv[l][i]; else vght[0][n]=0.;
114        i++;
115        for (m=1; m<=n; m++) {
116            vgh[m][n]=rf[l][i];
117            if (n<=8) vght[m][n]=sv[l][i]; else vght[m][n]=0.;
118            i++;
119            vgh[n][m-1]=rf[l][i];
120            if (n<=8) vght[n][m-1]=sv[l][i]; else vght[n][m-1]=0.;
121            i++;
122        }
123    }
124    field(6378.16, 298.25, 6371.2, maxod);
125    tcoef(vgh, vght, tzero, 0, dmy); tyear(year);
126}
127
128void sdgrf(double year)
129{   int i, n, m, l;
130    double dmy[3];
131    l=(int)(year-1945.)/5; if (l < 0) l=0; else if (l >= 9) l=8;
132    if ((year<1945.) || (year>1990.))
133        fprintf(stderr, "sdgrf: DGRF not available for %8.3lf\n", year);
134    for (i=0,n=1; n<=10; n++) {
135        vgh[0][n]=df[l][i]; vght[0][n]=(df[l+1][i]-df[l][i])/5.; i++;
136        for (m=1; m<=n; m++) {
137            vgh[m][n]=df[l][i]; vght[m][n]=(df[l+1][i]-df[l][i])/5.; i++;
138            vgh[n][m-1]=df[l][i]; vght[n][m-1]=(df[l+1][i]-df[l][i])/5.; i++;
139        }
140    }
141    field(6378.16, 298.25, 6371.2, 10);
142    tcoef(vgh, vght, (double)(1945+l*5), 0, dmy); tyear(year);
143}
144
145void spgrf(double year)
146{   int i, n, m, l;
147    double dmy[3];
148    l=(int)(year-1945.)/5; if (l < 6) l=6; else if (l >= 10) l=9;
149    if ((year<1975.) || (year>1995.))
150        fprintf(stderr, "spgrf: PGRF not available for %8.3lf\n", year);
151    for (i=0,n=1; n<=10; n++) {
152        vgh[0][n]=df[l][i]; vght[0][n]=(rf[l-4][i]-df[l][i])/5.; i++;
153        for (m=1; m<=n; m++) {
154            vgh[m][n]=df[l][i]; vght[m][n]=(rf[l-4][i]-df[l][i])/5.; i++;
155            vgh[n][m-1]=df[l][i]; vght[n][m-1]=(rf[l-4][i]-df[l][i])/5.; i++;
156        }
157    }
158    field(6378.16, 298.25, 6371.2, 10);
159    tcoef(vgh, vght, (double)(1945+l*5), 0, dmy); tyear(year);
160}
161
162void gigrf_(int *gen, float *year) { gigrf(*gen, (double)*year); }
163void igrfc_(float *fi, float *fk, float *h, float *f)
164    { double df; igrfc((double)*fi,(double)*fk,(double)*h,&df); *f=df; }
165void igrfm_(float fm[6])
166    { double dfm[6]; int i; igrfm(dfm); for (i=0; i<6; i++) fm[i]=dfm[i]; }
167void sigrf_(float *year) { sigrf((double)*year); }
168void sdgrf_(float *year) { sdgrf((double)*year); }
169void spgrf_(float *year) { spgrf((double)*year); }
170
171コード
172```### 前提・実現したいこと
173igrfによる磁場を計算するプログラムを学習しています
174### 発生している問題・エラーメッセージ
175
176c:/mingw/bin/../lib/gcc/mingw32/9.2.0/../../../../mingw32/bin/ld.exe: c:/mingw/bin/../lib/gcc/mingw32/9.2.0/../../../libmingw32.a(main.o):(.text.startup+0xc0): undefined reference to `WinMain@16'
177collect2.exe: error: ld returned 1 exit status
178
179### 該当のソースコード
180
181### 試したこと
182先生から型誓言がないといわれましたがよく分からないです
183### 補足情報（FW/ツールのバージョンなど）
184visualstudiocodeで実行しています。
185他のソースはコンパイルから実行まで上手くいきました。