Executable programs sometimes do not record the directories of the source files from which they were compiled, just the names. Even when they do, the directories could be moved between the compilation and your debugging session. gdb has a list of directories to search for source files; this is called the source path. Each time gdb wants a source file, it tries all the directories in the list, in the order they are present in the list, until it finds a file with the desired name. Note that the executable search path is not used for this purpose. Neither is the current working directory, unless it happens to be in the source path.
If gdb cannot find a source file in the source path, and the object program records a directory, gdb tries that directory too. If the source path is empty, and there is no record of the compilation directory, gdb looks in the current directory as a last resort.
Whenever you reset or rearrange the source path, gdb clears out any information it has cached about where source files are found and where each line is in the file.
When you start gdb, its source path includes only cdir and cwd, in that order. To add other directories, use the directory command.
Add directory dirname to the front of the source path. Several directory names may be given to this command, separated by : (; on MS-DOS and MS-Windows, where : usually appears as part of absolute file names) or whitespace. You may specify a directory that is already in the source path; this moves it forward, so gdb searches it sooner.
You can use the string $cdir to refer to the compilation directory (if one is recorded), and $cwd to refer to the current working directory. $cwd is not the same as .--the former tracks the current working directory as it changes during your gdb session, while the latter is immediately expanded to the current directory at the time you add an entry to the source path.
Reset the source path to empty again. This requires confirmation.
Print the source path: show which directories it contains.
If your source path is cluttered with directories that are no longer of interest, gdb may sometimes cause confusion by finding the wrong versions of source. You can correct the situation as follows:
Use directory with no argument to reset the source path to empty.
Use directory with suitable arguments to reinstall the directories you want in the source path. You can add all the directories in one command.