gcc-warning

I'm learning Pthreads. My code executes the way I want it to, I'm able to use it. But it gives me a warning on compilation. I compile using: gcc test.c -o test -pthread with GCC 4.8.1. And I get the warning test.c: In function ‘main’: test.c:39:46: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] pthread_create(&(tid[i]), &attr, runner, (void *) i); ^ test.c: In function ‘runner’: test.c:54:22: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] int threadnumber = (int) param; ^ This error comes for the following code: #include

This question already has an answer here: Compiler not detecting obviously uninitialized variable 4 answers I was reading some code from a book, when I decided to make a change to see what the uninitialized value of sec would be before the while statement: #include<stdio.h> #define S_TO_M 60 int main(void) { int sec,min,left; printf("This program converts seconds to minutes and "); printf("seconds. \n"); printf("Just enter the number of seconds. \n"); printf("Enter 0 to end the program. \n"); printf("sec = %d\n",sec); while(sec > 0) { scanf("%d",&sec); min = sec/S_TO_M; left = sec % S_TO_M;

When I compiled my C++ code with GCC 4.3 for the first time, (after having compiled it successfully with no warnings on 4.1, 4.0, 3.4 with the -Wall -Wextra options) I suddenly got a bunch of errors of the form warning: type qualifiers ignored on function return type . Consider temp.cpp : class Something { public: const int getConstThing() const { return _cMyInt; } const int getNonconstThing() const { return _myInt; } const int& getConstReference() const { return _myInt; } int& getNonconstReference() { return _myInt; } void setInt(const int newValue) { _myInt = newValue; } Something() :

#include <stdio.h> volatile int i; int main() { int c; for (i = 0; i < 3; i++) { c = i &&& i; printf("%d\n", c); } return 0; } The output of the above program compiled using gcc is 0 1 1 With the -Wall or -Waddress option, gcc issues a warning: warning: the address of ‘i’ will always evaluate as ‘true’ [-Waddress] How is c being evaluated in the above program? It's c = i && (&i); , with the second part being redundant, since &i will never evaluate to false . For a user-defined type, where you can actually overload unary operator & , it might be different, but it's still a very bad idea . If