GNU C Compiler Internals/GCC Hacks

Function overloading as in C++ This example was presented previously. toString() method for each structure as in Java Invoke a block of code from a function as in Ruby Linux implementation of lists allows to invoke a block of code on each element of the list: pagelist.c: list_for_each_prev(pos, head) { struct nfs_page *p = nfs_list_entry(pos); if (page_index(p->wb_page) < pg_idx) break; } list_for_each_prev takes the code in the brackets as a parameter. The trick is to use a macro that rolls out to a for() loop whose body becomes the code in the brackets. The goal of this project is to allow programmers to use code blocks in function calls. Dereference function results when a structure is returned C allows one to dereference the return value of a function if it is a pointer to a structure: get_struct()->field=0; If the function returns the structure, not a pointer to it, then a compile-time error is generated: get_struct().field=0; > request for member `field' in something not a structure or union This extension addresses the problem of dereferencing structures that are return values. Use functions to initialize a variable When a variable is defined and initialized the initializers is constant. You will get an error if you try to use a function, no matter what this function is: int getint() { return 1; } int i=getint(); > initializer element is not constant When a variable is used the function it was initialized with is called. Default values of function arguments as in C++ void func(int a=0) { printf("a=%d\n", a); } int main() { func(); } > syntax error before '=' token Reference parameters as in C++ void test(int &a, int &b); int x,y; test(x,y); Return address protection (RAD) Rad Repair of control-hijacking attacks (DIRA) Dira Array bounds checking using segmentation hardware (CASH) Cash Detecting interger overflows (DIVINE) Divine Develop in userland, install in kernel (DUSK) Dusk Dynamic Information Flow Tracking (GDIF) Gdif GCC switches in object file GCC switches in object file The -fstack-protector feature GCC 4.1 implements a protection mechanism against buffer overflow attacks and exposes it to a programmer with a -fstack-protector option. This is an example of functionality that benefits from modular implementation because it has nothing to do with core functionality of the compiler. Does GCC have enough hooks to implement -fstack-protector module? Function Overloading in C GCC Hacks Links