So you have OldLib with
void func1();
int func2();
... etc
The step 4 might look like creating another library with some static initialization.
Create NewLib with contents:
void your_func1();
void (*old_func1_ptr)() = NULL;
int (*old_func2_ptr)() = NULL;
void func1()
{
// in case you don't have static initializers, implement lazy loading
if(!old_func1_ptr)
{
void* lib = dlopen("OldLibFileName.so", RTLD_NOW);
old_func1_ptr = dlsym(lib, "func1");
}
old_func1_ptr();
}
int func2()
{
return old_func2_ptr();
}
// gcc extension, static initializer - will be called on .so's load
// If this is not supported, then you should call this function
// manually after loading the NewLib.so in your program.
// If the user of OldLib.so is not _your_ program,
// then implement lazy-loading in func1, func2 etc. - check function pointers for being NULL
// and do the dlopen/dlsym calls there.
__attribute__((constructor))
void static_global_init()
{
// use dlfcn.h
void* lib = dlopen("OldLibFileName.so", RTLD_NOW);
old_func1_ptr = dlsym(lib, "func1");
...
}
The static_global_init
and all the func_ptr
's can be autogenerated if you have some description of the old API. After the NewLib is created, you certainly can replace the OldLib.