CODEWITHSUNDEEP
c++cdllloadlibraryone-definition-rule
Aart Odding
Aart Odding

Reputation: 133

Does one definition rule apply to dynamically loading shared libraries at runtime?

If I load a dll or so library at runtime using dlopen() on unix or LoadLibrary() on windows, do i need to ensure that the symbols in the library do not have the same names as symbols in my program? Also is it possible to load multiple shared libraries that define the same functions?

Edit: I am specifically asking about runtime dynamic linking.

Upvotes: 5

Views: 789

Answers (1)

dbush
dbush

Reputation: 224082

Objects in a shared library loaded by dlopen do not appear in the namespace of the main program. You need to call dlsym with the name of the object as a string to get a pointer to it.

Using your example of having two libraries dynamically loaded having a global with the same name:

void *lib1 = dlopen("lib1.so", RTLD_LAZY);
int *lib1_global1 = dlsym(lib1, "global1");

void *lib2 = dlopen("lib2.so", RTLD_LAZY);
int *lib2_global1 = dlsym(lib2, "global1");

Here, both lib1.so and lib2.so contain a global variable of type int named global1. Because the dlsym function returns a pointer to the variable/function in question, you can handle this case with no conflict.

Upvotes: 2

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