c - Purpose of void* -

i trying understand casting in c. tried this code in ideone , got no errors @ all:

#include <stdio.h>  int main(void) {      int i=1;     char c = 'c';     float f = 1.0;      double* p = &i;     printf("%d\n",*(int*)p);     p = &c;     printf("%c\n",*(char*)p);     p = &f;     printf("%f\n",*(float*)p);     return 0; } 

but when compiled on c++ compiler here got these errors:

prog.cpp:9:15: error: cannot convert 'int*' 'double*' in initialization   double* p = &i;                ^ prog.cpp:11:4: error: cannot convert 'char*' 'double*' in assignment   p = &c;     ^ prog.cpp:13:4: error: cannot convert 'float*' 'double*' in assignment   p = &f;     ^ 

and compatible know far; is, can't assign (in c++) incompatible types pointer, void *, did here:

#include <stdio.h>  int main(void) {      int i=1;     char c = 'c';     float f = 1.0;      void* p = &i;     printf("%d\n",*(int*)p);     p = &c;     printf("%c\n",*(char*)p);     p = &f;     printf("%f\n",*(float*)p);     return 0; } 

now, if code runs in c, why need void pointer? can use kind of pointer want , cast when needed. read void pointer helps in making code generic accomplished if treat char * default pointer, wouldn't it?

try compile code serious ansi c compiler, c89 c11, , same error:

test.c(9): error #2168: operands of '=' have incompatible types 'double *' , 'int *'. test.c(11): error #2168: operands of '=' have incompatible types 'double *' , 'char *'. test.c(13): error #2168: operands of '=' have incompatible types 'double *' , 'float *'. 

i suppose online compiler trimmed accept code pre-ansi.
c still weak typed language, such errors not accepted actual standard level.
c++ more strong typed language (it needs work), online compielr gives error.
need of universal pointer, void *, absolutely required act general pointer interchanged.