I thought that if any C compilers for 8051/52 that is support ANSI standard, it should be compiled the other as well as long as the source and header file that requires go with it.

Do I missing something here. or is there any "trick" can get arround to work for those claimed C (ANSI) compilers ??

A fully ANSI C compliant C compiler for the '51 would be a disaster. Kernighan and Ritchie worked on large computers.

The memory structure of the '51 requires expansions to the C language to make the '51 run faster than a snail. The extensions are somewhat different for the various compilers, but realizing the reason makes it fairly easy to handle the differences.

I believe most seasoned '51 programmers have a .h file looking something like this
#define UD8 unsgined short data
#define UI8 unsigned short idata
#define UX8 unsigned short xdata
...
etc

Using this technique you can usually switch compilers quite easily.

Have fun,

Erik