Day by day I realise that I don't know C

I think it should be
double max (double x, double y) {
...

And ℅Lf in printf.

I'm amazed that gcc compiled without any errors. But g++ shows the error.

@lucas22 I'm not trying to debug it. I'm trying to figure out why this works.

@perix2 if I use int, I'll get a single output which will be 20 due to float to int implicit conversion. But I'm getting some garbage values each time I try to execute it.

@prabhakaran9397 that's probably because you're not actually declaring x and y, so what the compiler does is get random recent values that sometimes happen to be the correct ones. If there's one thing I've learned with C is that GCC warnings sucks and common errors are inexistent. I always use g++ or some other like clang.

Where did you learn that? Not declaring the type of the parameters predates the ANSI standard. That's really archaic, nobody declares their parameters like that any more, not for a long time. Last time I saw code like that it was from the 80s. I'm kind of surprised the compiler didn't warn about it.

Don't use undefined behaviour. If it happens, the compiler would not be violating the standard if it wiped your hard drive when you ran it.

Default int as said by @QoolQuy2000. the compiler feeds data laid out like a float in memory to a function that treats the same memory as an int.

Even if you don't use the stdlib, C++ keeps you safer by default.

And no matter which, always -Wall

¯\_(ツ)_/¯ you coming from python or something ?

@QoolQuy2000 while learning compiler design!

@Tychus trying to learn how GCC was designed and how it differs from G++ in parser phase

@TktStatusPICNIC wondering why they allowed those stupid stuffs!!!