invoking gdb

【invoking gdb】

The most usual way to start gdb is with one argument, specifying an executable program:

     gdb program

You can also start with both an executable program and a core file specified:

     gdb program core

You can, instead, specify a process ID as a second argument, if you want to debug a running process:

     gdb program 1234

would attach gdb to process 1234 (unless you also have a file named 1234; gdb does check for a core file first).

You can optionally have gdb pass any arguments after the executable file to the inferior using --args. This option stops option processing.

     gdb --args gcc -O2 -c foo.c

This will cause gdb to debug gcc, and to set gcc's command-line arguments (see Arguments) to ‘-O2 -c foo.c’.

【Index Files Speed Up gdb】

When gdb finds a symbol file, it scans the symbols in the file in order to construct an internal symbol table. This lets most gdb operations work quickly—at the cost of a delay early on. For large programs, this delay can be quite lengthy, so gdb provides a way to build an index, which speeds up startup.

The index is stored as a section in the symbol file. gdb can write the index to a file, then you can put it into the symbol file using objcopy.

To create an index file, use the save gdb-index command:

save gdb-index  directory

Create an index file for each symbol file currently known by gdb. Each file is named after its corresponding symbol file, with ‘ .gdb-index’ appended, and is written into the given  directory.

Once you have created an index file you can merge it into your symbol file, here named symfile, using objcopy:

     $ objcopy --add-section .gdb_index=symfile.gdb-index \

         --set-section-flags .gdb_index=readonly symfile symfile

 参考：

　　1、https://sourceware.org/gdb/download/onlinedocs/gdb/Invoking-GDB.html#Invoking-GDB

　　2、https://sourceware.org/gdb/download/onlinedocs/gdb/Index-Files.html#Index-Files