### 16.3 Host Misc

`FATAL_EXIT_CODE`
  A C expression for the status code to be returned when the compiler exits after serious errors. The default is the system-provided macro ‘`EXIT_FAILURE`’, or ‘`1`’ if the system doesn't define that macro. Define this macro only if these defaults are incorrect.
`SUCCESS_EXIT_CODE`
  A C expression for the status code to be returned when the compiler exits without serious errors. (Warnings are not serious errors.) The default is the system-provided macro ‘`EXIT_SUCCESS`’, or ‘`0`’ if the system doesn't define that macro. Define this macro only if these defaults are incorrect.
`USE_C_ALLOCA`
  Define this macro if GCC should use the C implementation of `alloca` provided by `libiberty.a`. This only affects how some parts of the compiler itself allocate memory. It does not change code generation.

  When GCC is built with a compiler other than itself, the C `alloca` is always used. This is because most other implementations have serious bugs. You should define this macro only on a system where no stack-based `alloca` can possibly work. For instance, if a system has a small limit on the size of the stack, GCC's builtin `alloca` will not work reliably.

`COLLECT2_HOST_INITIALIZATION`
  If defined, a C statement (sans semicolon) that performs host-dependent initialization when `collect2` is being initialized.
`GCC_DRIVER_HOST_INITIALIZATION`
  If defined, a C statement (sans semicolon) that performs host-dependent initialization when a compilation driver is being initialized.
`HOST_LONG_LONG_FORMAT`
  If defined, the string used to indicate an argument of type `long long` to functions like `printf`. The default value is `"ll"`.

In addition, if `configure` generates an incorrect definition of any of the macros in `auto-host.h`, you can override that definition in a host configuration header. If you need to do this, first see if it is possible to fix `configure`.