Parameters

Parameter

 

Definition

 

 

 

handle

A pointer to a shared library handle of the library to search for the symbol name sym. This handle

 

can be obtained from the shl_get routine (“The shl_get and shl_get_r Routines” (page 175)). The

 

handle parameter can also point to:

 

 

 

 

NULL

If a pointer to NULL is specified, shl_findsym searches all loaded

 

 

libraries for sym. If sym is found, shl_findsym sets handle to a

 

 

pointer to the handle of the shared library containing sym. This is useful

 

 

for determining which library a symbol resides in. For example, the

 

 

following code sets handle to a pointer to the handle of the library

 

 

containing symbol_foo

 

 

shl_t handle;

 

 

handle = NULL;

 

 

shl_findsym(&handle,"_foo",...);

 

 

 

 

PROG_HANDLE

This constant, defined in dl.h, tells shl_findsym to search for the

 

 

symbol in the program itself. This way, any symbols exported from the

 

 

program can be accessed explicitly.

 

 

 

sym

A null-terminated character string containing the name of the symbol to search for.

 

 

 

type

The type of symbol to look for. It must be one of the following values, defined in <dl.h>:

 

 

 

 

TYPE_PROCEDURE

Looks for a function or procedure.

 

 

 

 

TYPE_DATA

Looks for a symbol in the data segment (for example, variables).

 

 

 

 

TYPE_UNDEFINED

Looks for any symbol.

 

 

 

 

TYPE_STORAGE

Same as TYPE_DATA

 

 

 

value

A pointer in which shl_findsym stores the address of sym, if found.

 

 

 

Return Value

If successful, shl_findsym returns an integer (int) value zero. If shl_findsym cannot find sym, it returns -1and sets errno to zero. If any other errors occur, shl_findsym returns -1 and sets errno to one of these values (defined in <errno.h>):

Parameter

Definition

 

 

ENOEXEC

A format error was detected in the specified library.

 

 

ENOSYM

A symbol on which sym depends cannot be found.

 

 

EINVAL

The specified handle is invalid.

 

 

Description

To call a routine or access data in an explicitly loaded library, first get the address of the routine or data with shl_findsym. To call a routine in an explicitly loaded library:

1.Declare a pointer to a function of the same type as the function in the shared library

2.Using shl_findsym with the type parameter set to TYPE_PROCEDURE, find the symbol in the shared library and assign its address to the function pointer declared in Step 1

3.Call the pointer to the function obtained in Step 2, with the correct number and type of arguments

To access data in an explicitly loaded library:

The shl_load Shared Library Management Routines 173