21.6. Configuring the current ABI

gdb can determine the ABI (Application Binary Interface) of your application automatically. However, sometimes you need to override its conclusions. Use these commands to manage gdb's view of the current ABI.

One gdb configuration can debug binaries for multiple operating system targets, either via remote debugging or native emulation. gdb will autodetect the OS ABI (Operating System ABI) in use, but you can override its conclusion using the set osabi command. One example where this is useful is in debugging of binaries which use an alternate C library (e.g. uClibc for gnu/Linux) which does not have the same identifying marks that the standard C library for your platform provides.

Generally, the way that an argument of type float is passed to a function depends on whether the function is prototyped. For a prototyped (that is, ANSI/ISO style) function, float arguments are passed unchanged, according to the architecture's convention for float. For unprototyped (that is, K&R style) functions, float arguments are first promoted to type double and then passed.

Unfortunately, some forms of debug information do not reliably indicate whether a function is prototyped. If gdb calls a function that is not marked as prototyped, it consults set coerce-float-to-double.

gdb needs to know the ABI used for your program's C++ objects. The correct C++ ABI depends on which C++ compiler was used to build your application. gdb only fully supports programs with a single C++ ABI; if your program contains code using multiple C++ ABI's or if gdb can not identify your program's ABI correctly, you can tell gdb which ABI to use. Currently supported ABI's include "gnu-v2", for g++ versions before 3.0, "gnu-v3", for g++ versions 3.0 and later, and "hpaCC" for the HP ANSI C++ compiler. Other C++ compilers may use the "gnu-v2" or "gnu-v3" ABI's as well. The default setting is "auto".