Stack Smashing Protection (GNU Compiler Collection (GCC) Internals)

#### 19.9.15 Stack smashing protection ¶

Target Hook: `tree` TARGET_STACK_PROTECT_GUARD `(void)` ¶

  This hook returns a `DECL` node for the external variable to use for the stack protection guard. This variable is initialized by the runtime to some random value and is used to initialize the guard value that is placed at the top of the local stack frame. The type of this variable must be `ptr_type_node`.

  The default version of this hook creates a variable called ‘`__stack_chk_guard`’, which is normally defined in `libgcc2.c`.

Target Hook: `tree` TARGET_STACK_PROTECT_FAIL `(void)` ¶

  This hook returns a `CALL_EXPR` that alerts the runtime that the stack protect guard variable has been modified. This expression should involve a call to a `noreturn` function.

  The default version of this hook invokes a function called ‘`__stack_chk_fail`’, taking no arguments. This function is normally defined in `libgcc2.c`.

Target Hook: `bool` TARGET_STACK_PROTECT_RUNTIME_ENABLED_P `(void)` ¶

  Returns true if the target wants GCC’s default stack protect runtime support, otherwise return false. The default implementation always returns true.

Common Target Hook: `bool` TARGET_SUPPORTS_SPLIT_STACK `(bool report, struct gcc_options *opts)` ¶

  Whether this target supports splitting the stack when the options described in opts have been passed. This is called after options have been parsed, so the target may reject splitting the stack in some configurations. The default version of this hook returns false. If report is true, this function may issue a warning or error; if report is false, it must simply return a value

Common Target Hook: `vec<const char *>` TARGET_GET_VALID_OPTION_VALUES `(int option_code, const char *prefix)` ¶

  The hook is used for options that have a non-trivial list of possible option values. OPTION_CODE is option code of opt_code enum type. PREFIX is used for bash completion and allows an implementation to return more specific completion based on the prefix. All string values should be allocated from heap memory and consumers should release them. The result will be pruned to cases with PREFIX if not NULL.