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#### 15.4.1.7 GDB Features for C`++`

Some GDB commands are particularly useful with C`++`, and some are designed specifically for use with C`++`. Here is a summary:

`breakpoint menus`

  When you want a breakpoint in a function whose name is overloaded, GDB has the capability to display a menu of possible breakpoint locations to help you specify which function definition you want. See Ambiguous Expressions.

`rbreak regex`

  Setting breakpoints using regular expressions is helpful for setting breakpoints on overloaded functions that are not members of any special classes. See Setting Breakpoints.

`catch throw`
`catch rethrow`
`catch catch`

  Debug C`++` exception handling using these commands. See Setting Catchpoints.

`ptype typename`

  Print inheritance relationships as well as other information for type typename. See Examining the Symbol Table.

`info vtbl expression.`

  The `info vtbl` command can be used to display the virtual method tables of the object computed by expression. This shows one entry per virtual table; there may be multiple virtual tables when multiple inheritance is in use.

`demangle name`

  Demangle name. See Examining the Symbol Table, for a more complete description of the `demangle` command.

`set print demangle`
`show print demangle`
`set print asm-demangle`
`show print asm-demangle`

  Control whether C`++` symbols display in their source form, both when displaying code as C`++` source and when displaying disassemblies. See Print Settings.

`set print object`
`show print object`

  Choose whether to print derived (actual) or declared types of objects. See Print Settings.

`set print vtbl`
`show print vtbl`

  Control the format for printing virtual function tables. See Print Settings. (The `vtbl` commands do not work on programs compiled with the HP ANSI C`++` compiler (`aCC`).)

`set overload-resolution on`

  Enable overload resolution for C`++` expression evaluation. The default is on. For overloaded functions, GDB evaluates the arguments and searches for a function whose signature matches the argument types, using the standard C`++` conversion rules (see C`++` Expressions, for details). If it cannot find a match, it emits a message.

`set overload-resolution off`

  Disable overload resolution for C`++` expression evaluation. For overloaded functions that are not class member functions, GDB chooses the first function of the specified name that it finds in the symbol table, whether or not its arguments are of the correct type. For overloaded functions that are class member functions, GDB searches for a function whose signature exactly matches the argument types.

`show overload-resolution`

  Show the current setting of overload resolution.

`Overloaded symbol names`

  You can specify a particular definition of an overloaded symbol, using the same notation that is used to declare such symbols in C`++`: type `symbol(types)` rather than just symbol. You can also use the GDB command-line word completion facilities to list the available choices, or to finish the type list for you. See Command Completion, for details on how to do this.

`Breakpoints in template functions`

  Similar to how overloaded symbols are handled, GDB will ignore template parameter lists when it encounters a symbol which includes a C`++` template. This permits setting breakpoints on families of template functions or functions whose parameters include template types.

  The `-qualified` flag may be used to override this behavior, causing GDB to search for a specific function or type.

  The GDB command-line word completion facility also understands template parameters and may be used to list available choices or finish template parameter lists for you. See Command Completion, for details on how to do this.

`Breakpoints in functions with ABI tags`

  The GNU C`++` compiler introduced the notion of ABI “tags”, which correspond to changes in the ABI of a type, function, or variable that would not otherwise be reflected in a mangled name. See https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/ for more detail.

  The ABI tags are visible in C`++` demangled names. For example, a function that returns a std::string:

      std::string function(int);

  when compiled for the C++11 ABI is marked with the `cxx11` ABI tag, and GDB displays the symbol like this:

      function[abi:cxx11](int)

  You can set a breakpoint on such functions simply as if they had no tag. For example:

      (gdb) b function(int)
      Breakpoint 2 at 0x40060d: file main.cc, line 10.
      (gdb) info breakpoints
      Num     Type           Disp Enb Address    What
      1       breakpoint     keep y   0x0040060d in function[abi:cxx11](int)
                                                 at main.cc:10

  On the rare occasion you need to disambiguate between different ABI tags, you can do so by simply including the ABI tag in the function name, like:

      (gdb) b ambiguous[abi:other_tag](int)

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