I am confused by the commands set solib-search-path and set sysroot, not sure when to use one or another. In my case symbols are only loaded when i used both the commands. Is it always both the commands are required and what does each command does.
For here http://visualgdb.com/gdbreference/commands/, it looks like sysroot looks in subdirectories too, then why is solib-search-path required, if both search for libraries and load symbols from those libraries
gdb searches first for libraries in sysroot (with an absolute path), and then only if it fails to find them it searches into solib-search-path (with a relative path).
For that reason, when using gdb server / remote debugging you probably want to use ONLY gdb's sysroot option. On a Linux system using solib-search-path will NOT work unless you change the value of sysroot, because the default value of sysroot is target, meaning that gdb is loading the so-file found on the filesystem you are debugging. This is also what is indicated in gdb's documentation:
set solib-search-path path
colon-separated list of directories to search for shared libraries. ‘solib-search-path’ is used after ‘sysroot’ fails to locate the library, or if the path to the library is relative instead of absolute. If you want to use ‘solib-search-path’ instead of ‘sysroot’, be sure to set ‘sysroot’ to a nonexistent directory to prevent GDB from finding your host’s libraries. ‘sysroot’ is preferred; setting it to a nonexistent directory may interfere with automatic loading of shared library symbols.
As indicated in this thread, the use-case for solib-search-path is rather:
solib-search-path is there mostly to help targets like Windows that don't report to the debugger the full path to the shared library. GNU/Linux always works with full patchs, such as "/usr/lib/libjpeg.so.8"
