gcc-warning

I learned from C Primer Plus that if you want to protect an array from being accidentally modified by a function, you should add const modifier before the pointer declaration in the header of function definition. Following this sensible advice, in the following minimal example, I'm trying to pass a non-constant two-dimensional array array to the function Sum2D , one parameter of which is a pointer-to-const-int[2] . #include <stdio.h> #define ROWS 2 #define COLS 2 int Sum2D(const int ar[][COLS], int rows); //use `const` to protect input array int main(void) { int array[ROWS][COLS]={{1,2},{3,4}}

I'm getting a number of these warnings when compiling a few binaries: warning: incompatible implicit declaration of built-in function ‘strcpy’ warning: incompatible implicit declaration of built-in function ‘strlen’ warning: incompatible implicit declaration of built-in function ‘exit’ To try to resolve this, I have added #include <stdlib.h> at the top of the C files associated with this warning, in addition to compiling with the following flags: CFLAGS = -fno-builtin-exit -fno-builtin-strcat -fno-builtin-strncat -fno-builtin-strcpy -fno-builtin-strlen -fno-builtin-calloc I am using GCC 4.1.2:

I would like to enable -- literally -- ALL of the warnings that GCC has. (You'd think it would be easy...) You'd think -Wall might do the trick, but nope! Still need -Wextra . You'd think -Wextra might do the trick, but nope! Not all of the warnings listed here (for example, -Wshadow ) are enabled by this. And I still have no idea if this list is comprehensive. How do I tell GCC to enable (no if's, and's, or but's!) all the warnings it has? You can't. The manual for GCC 4.4.0 is only comprehensive for that version, but it does list all the possible warnings for 4.4.0. They're not all on the

For instance: Bool NullFunc(const struct timespec *when, const char *who) { return TRUE; } In C++ I was able to put a /*...*/ comment around the parameters. But not in C of course, where it gives me the error error: parameter name omitted . Job I usually write a macro like this: #define UNUSED(x) (void)(x) You can use this macro for all your unused parameters. (Note that this works on any compiler.) For example: void f(int x) { UNUSED(x); ... } Flow In gcc, you can label the parameter with the unused attribute . This attribute, attached to a variable, means that the variable is meant to be

I have a project that uses log4cxx, boost, etc. libraries whose headers generate lots of (repetitive) warnings. Is there a way to suppress warnings from library includes (i.e. #include <some-header.h>) or includes from certain paths? I'd like to use -Wall and/or -Wextra as usual on project code without relevant info being obscured. I currently use grep on make output but I'd like something better. Phi You may try to include library headers using -isystem instead of -I . This will make them "system headers" and GCC won't report warnings for them. For those using CMake, you can modify your

The code below performs a fast inverse square root operation by some bit hacks. The algorithm was probably developed by Silicon Graphics in early 1990's and it's appeared in Quake 3 too. more info However I get the following warning from GCC C++ compiler : dereferencing type-punned pointer will break strict-aliasing rules Should I use static_cast , reinterpret_cast or dynamic_cast instead in such situations? float InverseSquareRoot(float x) { float xhalf = 0.5f*x; int32_t i = *(int32_t*)&x; i = 0x5f3759df - (i>>1); x = *(float*)&i; x = x*(1.5f - xhalf*x*x); return x; } Forget casts. Use memcpy