c-gcc, 76 bytes

Result

WA

Code [DL]

f(char*a,char*b){x=*a-*b;}s[100],x;main(){gets(s);qsort(s,100,1,f);puts(s);}

stdin

4269071708387161720654350100738886026716876713561686778686977549850884473923694526887821512042684036

stdout

stderr

/volume/CODE.c:1:1: warning: return type defaults to ‘int’ [-Wimplicit-int]
 f(char*a,char*b){x=*a-*b;}s[100],x;main(){gets(s);qsort(s,100,1,f);puts(s);}
 ^
/volume/CODE.c: In function ‘f’:
/volume/CODE.c:1:18: error: ‘x’ undeclared (first use in this function)
 f(char*a,char*b){x=*a-*b;}s[100],x;main(){gets(s);qsort(s,100,1,f);puts(s);}
                  ^
/volume/CODE.c:1:18: note: each undeclared identifier is reported only once for each function it appears in
/volume/CODE.c: At top level:
/volume/CODE.c:1:27: warning: data definition has no type or storage class
 f(char*a,char*b){x=*a-*b;}s[100],x;main(){gets(s);qsort(s,100,1,f);puts(s);}
                           ^
/volume/CODE.c:1:27: warning: type defaults to ‘int’ in declaration of ‘s’ [-Wimplicit-int]
/volume/CODE.c:1:34: warning: type defaults to ‘int’ in declaration of ‘x’ [-Wimplicit-int]
 f(char*a,char*b){x=*a-*b;}s[100],x;main(){gets(s);qsort(s,100,1,f);puts(s);}
                                  ^
/volume/CODE.c:1:36: warning: return type defaults to ‘int’ [-Wimplicit-int]
 f(char*a,char*b){x=*a-*b;}s[100],x;main(){gets(s);qsort(s,100,1,f);puts(s);}
                                    ^
/volume/CODE.c: In function ‘main’:
/volume/CODE.c:1:43: warning: implicit declaration of function ‘gets’ [-Wimplicit-function-declaration]
 f(char*a,char*b){x=*a-*b;}s[100],x;main(){gets(s);qsort(s,100,1,f);puts(s);}
                                           ^
/volume/CODE.c:1:51: warning: implicit declaration of function ‘qsort’ [-Wimplicit-function-declaration]
 f(char*a,char*b){x=*a-*b;}s[100],x;main(){gets(s);qsort(s,100,1,f);puts(s);}
                                                   ^
/volume/CODE.c:1:68: warning: implicit declaration of function ‘puts’ [-Wimplicit-function-declaration]
 f(char*a,char*b){x=*a-*b;}s[100],x;main(){gets(s);qsort(s,100,1,f);puts(s);}
                                                                    ^
/volume/CODE.c: In function ‘f’:
/volume/CODE.c:1:1: warning: control reaches end of non-void function [-Wreturn-type]
 f(char*a,char*b){x=*a-*b;}s[100],x;main(){gets(s);qsort(s,100,1,f);puts(s);}
 ^
/home/esolang/bin/c-gcc: line 4: /tmp/code: No such file or directory

strace