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Dynload C library API

The dynload library encapsulates dynamic loading mechanisms and gives access to functions in foreign dynamic libraries and code modules.

Loading code

DLLib* dlLoadLibrary(const char* libpath); 
void  dlFreeLibrary(void* libhandle);

dlLoadLibrary loads a dynamic library at libpath and returns a handle to it for use in dlFreeLibrary and dlFindSymbol calls. Passing a null pointer for the libpath argument is valid, and returns a handle to the main executable of the calling code. Also, searching libraries in library paths (e.g. by just passing the library’s leaf name) should work, however, they are OS specific. Returns a null pointer on error.

dlFreeLibrary frees the loaded library with handle pLib.

Retrieving functions

void* dlFindSymbol(void* libhandle, const char* symbol);

This function returns a pointer to a symbol with name pSymbolName in the library with handle pLib, or returns a null pointer if the symbol cannot be found. The name is specified as it would appear in C source code (mangled if C++, etc.).

Misc functions

int dlGetLibraryPath(DLLib* pLib, char* sOut, int bufSize);

This function can be used to get a copy of the path to the library loaded with handle pLib. The parameter sOut is a pointer to a buffer of size bufSize (in bytes), to hold the output string. The return value is the size of the buffer (in bytes) needed to hold the null-terminated string, or 0 if it can’t be looked up. If bufSize ¿= return value ¿ 1, a null-terminted string with the path to the library should be in sOut. If it returns 0, the library name wasn’t able to be found. Please note that this might happen in some rare cases, so make sure to always check.

Symbol iteration

DLSyms*     dlSymsInit(const char* libPath); 
void        dlSymsCleanup(DLSyms* pSyms); 
int         dlSymsCount(DLSyms* pSyms); 
const char* dlSymsName(DLSyms* pSyms, int index); 
const char* dlSymsNameFromValue(DLSyms* pSyms, void* value); /* symbol must be loaded */

These functions can be used to iterate over symbols. Since they can be used on libraries that are not linked, they are made for symbol name lookups, not to get a symbol’s address. For that refer to dlFindSymbol. dlSymsInit will return a handle (or a null pointer on error) to the shared object specified by libPath, to be used with the other dlSyms* functions. Note that contrary to loading and linking libraries, no (OS-specific) rules for searching libraries in library paths, etc. apply. The handle must be freed with dlSymsCleanup. dlSymsCount returns the number of symbols in the shared object, dlSymsName and dlSymsNameFromValue are used to lookup symbol names using an index or symbol’s address, respectively, returning a null pointer on error. The names are returned as they would appear in C source code (mangled if C++, etc.). The address passed to dlSymsNameFromValue must point to a loaded symbol.


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