dlgetfileinfo(3C)dlgetfileinfo(3C)NAMEdlgetfileinfo() - return file information for a library prior to load‐
ing it
SYNOPSIS
[flag... ] file... [library]...
uint64_t dlgetfileinfo(const char *file,
size_t info_size,
struct dlfileinfo *info);
Multithread Usage
This routine is thread-safe.
DESCRIPTION
is one of a family of routines that give the user direct access to the
dynamic linking facilities (using the option on the compiler or command
line). returns file information for a library prior to loading it.
This information can be used to allocate load segments before calling
file is used to construct a path name to the library. The dynamic
loader searches for the library using the standard search rules used by
and If the library is found and is a valid shared library, returns
information about the library through the info parameter.
info_size is the size in bytes of the info buffer.
info is a pointer to a buffer allocated by the user program. The
dynamic loader fills this buffer with file information.
A dlfileinfo structure has the following members:
struct dlfileinfo {
size_t text_size;
size_t data_size;
char *filename;
}
text_size is the size in bytes of a shared library's text segment.
data_size is the size in bytes of a shared library's data segment.
filename is the path to the shared library. This path may be passed to
a subsequent or call to avoid searching for the library a second time.
The caller of must copy the value of filename to insure that it is not
corrupted.
EXAMPLES
The following example illustrates the use of to allocate memory for
mapping a shared library's data segment. For simplicity, error check‐
ing has been omitted.
#include <dlfcn.h>
#include <string.h>
/* allocate_data is a user-supplied routine that allocates a
* a memory buffer of at least "data_size" bytes and returns
* a pointer to the buffer.
*/
extern char *allocate_data(size_t data_size);
int main() {
void *handle;
int status;
char *pathname;
struct dlfileinfo info;
struct dlopen_opts opts;
/* Locate library and get file information */
status = dlgetfileinfo("mylib.so", sizeof(info), &info);
if (status == 0) {
/* Make a copy of the library pathname returned by
* dlgetfileinfo().
*/
pathname = strdup(info.filename);
/* Allocate data segment */
opts.data_addr = allocate_data(info.data_size);
/* Not preallocating text segment */
opts.text_addr = 0;
/* Set dlopene() flags to indicate the data segment
* has been preallocated.
*/
opts.flags = RTLD_EXT_DATA_ADDR;
/* Call dlopene() to load the library using the path
* where dlgetfileinfo found the library and the
* preallocated memory buffer for mapping the library's
* data segment.
*/
handle = dlopene(pathname, RTLD_LAZY, &opts);
/* Remove copy of library pathname */
free(pathname);
/* Insert code here to use library */
/* Close library */
status = dlclose(handle);
/* Insert code here to free storage allocated by
* allocate_data().
*/
}
}
RETURN VALUE
If successful, returns otherwise a non-0 value is returned. More
detailed diagnostic information is available through or
ERRORS
If fails, a subsequent call to returns one of the following values:
Unknown ELF version in library.
Unable to find library.
Cannot allocate dynamic memory.
Internal error encountered in
Failed to apply relocation while resolving call to
call failed on entry to
call failed on exit from
ABI mismatch because a 64-bit program found a 32-bit shared
library.
ABI mismatch because a 32-bit program found a 64-bit shared
library.
The library is invalid due to a bad magic number.
The library is invalid due to a bad machine type.
The library is invalid due to a bad object file type.
failed on entry to or exit from
Cannot return file information because the library has multiple
text segments.
Cannot return file information because the library has multiple
data segments.
Invalid argument in call to
An IO error occurred while reading the file information.
SEE ALSOdlerrno(3C), dlerror(3C), dlopen(3C), dlopene(3C), dlsetlibpath(3C).
Texts and Tutorials:
(See the option)
(See manuals(5) for ordering information)
dlgetfileinfo(3C)
