OS/2 codes: How to writes initialization/termination codes with gcc

When programming, one of the most annoying things is to write initialization/termination codes. In case of DLL, OS/2 provides the opportunity for this by _DLL_InitTerm(). However, if it is a static library, OS/2 does not provide any ways for this. Instead, compilers provides its own ways for this.

Of course, gcc has its own ways. They are __attribute__((consturctor)) for intialization and __attribute__((destructor)) for termination. Here are the sample code.

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#include <stdio.h> __attribute__((constructor)) static void before( void ) {     printf("constructor : before()\n"); } __attribute__((destructor)) static void after( void ) {     printf("destructor : after()\n"); } int main( void ) {     printf("main()\n");     return 0; }

If you run this program,  you can see the following.

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constructor : before() main() destructor : after()

However, be careful when linking DLL with customized _DLL_InitTerm(). The default codes of _DLL_InitTerm() are like this,

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unsigned long _System _DLL_InitTerm( unsigned long hmod, unsigned long flags ) {     switch( flags )     {         case 0 :             if( _CRT_init() == -1 )                 return 0;             __ctordtorInit();             break;         case 1 :             __ctordtorTerm();             _CRT_term();             break;         default :             return 0;     }     return 1; }

By the way, sometimes __ctordotrInit() and __ctordotrTerm() are missed because C++ codes are not used. But without them, functions declared with __attribute__((constructor)) and __attribute__((destructor)) are not called. So if you write DLLs and use cutomized _DLL_InitTerm(), it would be a good habit to call __ctordtorInit() and __ctordtorTerm() regardless of using C++ codes.