c89

Many times I want a function to receive a variable number of arguments, terminated by NULL, for instance #define push(stack_t stack, ...) _push(__VARARG__, NULL); func _push(stack_t stack, char *s, ...) { va_list args; va_start(args, s); while (s = va_arg(args, char*)) push_single(stack, s); } Can I instruct gcc or clang to warn if foo receives non char* variables? Something similar to __attribute__(format) , but for multiple arguments of the same pointer type. I know you're thinking of using __attribute__((sentinel)) somehow, but this is a red herring. What you want is to do something like

I work on a code base which is mostly C with a little C++, and is mostly built with gcc but occasionally it needs to be built with MSVC. Microsoft's C compiler is still pretty much C89 with a few minor extensions, and it still doesn't support mixed code and variable definitions à la C++/C99. So I need to find a way to prevent developers from writing out-of-order code/variable definitions while they are working with gcc, otherwise the build subsequently breaks with MSVC. If I use gcc -std=c89 then everything breaks because C++-style comments are not allowed (there may be other issues too, but I

I have an API with a publicly facing struct A and an internal struct B and need to be able to convert a struct B into a struct A. Is the following code legal and well defined behavior in C99 (and VS 2010/C89) and C++03/C++11? If it is, please explain what makes it well-defined. If it's not, what is the most efficient and cross-platform means for converting between the two structs? struct A { uint32_t x; uint32_t y; uint32_t z; }; struct B { uint32_t x; uint32_t y; uint32_t z; uint64_t c; }; union U { struct A a; struct B b; }; int main(int argc, char* argv[]) { U u; u.b.x = 1; u.b.y = 2; u.b.z

I'm trying to compile a linux kernel module using a Makefile: obj-m += main.o all: make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules clean: make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean Which gives me: main.c:54: warning: ISO C90 forbids mixed declarations and code I need to switch to C99. After reading I noticed I need to add a flag -std=c99, not sure where it suppose to be added. How do I change the Makefile so it will compile as C99? It's got nothing to do with the makefile. ISO C90 forbids declaring variables anywhere but in the beginning of a block or the file -