Debugging with GDB: Explicit Locations

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9.2.2 Explicit Locations

Explicit locations allow the user to directly specify the source location’s parameters using option-value pairs.

Explicit locations are useful when several functions, labels, or file names have the same name (base name for files) in the program’s sources. In these cases, explicit locations point to the source line you meant more accurately and unambiguously. Also, using explicit locations might be faster in large programs.

For example, the linespec ‘foo:bar’ may refer to a function bar defined in the file named foo or the label bar in a function named foo. GDB must search either the file system or the symbol table to know.

The list of valid explicit location options is summarized in the following table:

-source filename

The value specifies the source file name. To differentiate between files with the same base name, prepend as many directories as is necessary to uniquely identify the desired file, e.g., foo/bar/baz.c. Otherwise GDB will use the first file it finds with the given base name. This option requires the use of either -function or -line.

-function function

The value specifies the name of a function. Operations on function locations unmodified by other options (such as -label or -line) refer to the line that begins the body of the function. In C, for example, this is the line with the open brace.

By default, in C++ and Ada, function is interpreted as specifying all functions named function in all scopes. For C++, this means in all namespaces and classes. For Ada, this means in all packages.

For example, assuming a program with C++ symbols named A::B::func and B::func, both commands break -function func and break -function B::func set a breakpoint on both symbols.

You can use the -qualified flag to override this (see below).

-qualified

This flag makes GDB interpret a function name specified with -function as a complete fully-qualified name.

For example, assuming a C++ program with symbols named A::B::func and B::func, the break -qualified -function B::func command sets a breakpoint on B::func, only.

(Note: the -qualified option can precede a linespec as well (see Linespec Locations), so the particular example above could be simplified as break -qualified B::func .)

-label label

The value specifies the name of a label. When the function name is not specified, the label is searched in the function of the currently selected stack frame.

-line number

The value specifies a line offset for the location. The offset may either be absolute (-line 3) or relative (-line +3), depending on the command. When specified without any other options, the line offset is relative to the current line.

Explicit location options may be abbreviated by omitting any non-unique trailing characters from the option name, e.g., break -s main.c -li 3 .

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