Using dwarf_init_path_dl()

Example focused on GNU debuglink data.

In case GNU debuglink data is followed the true_pathbuf content will not match path. The path actually used is copied to true_path_out.

In the case of MacOS dSYM the true_path_out may not match path.

If debuglink data is missing from the Elf executable or shared-object (ie, it is a normal object!) or unusable by libdwarf or true_path_buffer len is zero or true_path_out_buffer is zero libdwarf accepts the path given as the object to report on, no debuglink or dSYM processing will be used.

See also

https://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-Files.html

An example calling dwarf_init_path_dl() and dwarf_finish()

Parameters

path	Path to an object we wish to open.
groupnumber	Desired groupnumber. Use DW_DW_GROUPNUMBER_ANY unless you have reason to do otherwise.
error	A pointer we can use to record error details.

Returns

Returns the applicable result. DW_DLV_OK etc.

*/
int exampleinit_dl(const char *path, unsigned groupnumber,
    Dwarf_Error *error)
{
    static char true_pathbuf[FILENAME_MAX];
    static const char *glpath[3] = {
        "/usr/local/debug",
        "/usr/local/private/debug",
        "/usr/local/libdwarf/debug"
    };
    unsigned      tpathlen = FILENAME_MAX;
    Dwarf_Handler errhand = 0;
    Dwarf_Ptr     errarg = 0;
    Dwarf_Debug   dbg = 0;
    int           res = 0;
    unsigned char path_source = 0;
 
    res = dwarf_init_path_dl(path,true_pathbuf,
        tpathlen,groupnumber,errhand,
        errarg,&dbg,
        (char **)glpath,
        3,
        &path_source,
        error);
    if (res == DW_DLV_ERROR) {
        /*  We are not returning dbg, so we must do:
            dwarf_dealloc_error(dbg,*error);
            here to free the error details. */
        dwarf_dealloc_error(dbg,*error);
        *error = 0;
        return res;
    }
    if (res == DW_DLV_NO_ENTRY) {
        return res;
    }
    printf("The file we actually opened is %s\n",
        true_pathbuf);
    /* Call libdwarf functions here */
    dwarf_finish(dbg);
    return res;
}