Interesting trivia

• index[array] ≡ array[index] ≡  *(array + index)
• arguments to a function may be evaluated in any order by the compiler
• The signed-ness of plain char is compiler-dependent

C99 Hotness

• Boolean type introduced:

#include <stdbool.h>
bool a = true, b = false;

• //-comments formally allowed
• declarations can go anywhere within a function; C89 forces you to declare everything at the start of the function

Syntax

#include <something_in_std_lib.h>
#include "your_own_lib.h"
enum SomeEnum {A, B, C};
typedef someDeclaration newTypeAlias;

• const keyword, like Java’s final
• static keyword means private to this source file, like C#’s internal

Basics

int main(int argc, char * argv[])
char aStringVariable[length];

• EXIT_SUCCESS, EXIT_FAILURE defined in stdlib.h

Function pointers

int foo(char);//declare function
int (*funcPtr)(char) = foo;
int result = funcPtr('a');//use func pointer

Objects

Defining

struct Foo
//unions use same syntax, just w/ different keyword
{
    int a;
    char b;
}

Using

/* C99: */ struct Foo bar = {.b = 'Q', .a = 42};
/* C89: */ struct Foo baz = {42, 'Q'};

Defining macros

• Function-like macros: #define foo(a,b) ((a)-(b))
• The ## operator within macros:
  • Given: #define foo(x) MSG_##x
  • Then: foo(A) ≡ MSG_A
• The # operator within macros – converts operand to string

Useful macros

Assertions:

#include <assert.h>
assert(booleanExpression);

• #define NDEBUG – disables asserts
• #error "Message" – causes compile error with given message
• Conditional compilation: #if, #elif, #else, #endif

Metadata macros

• __func__ – name of current function
• __LINE__ – current line number
• __FILE__ – name of current file
• __TIME__ – time of compilation
• __DATE__ – date of compilation

Standards macros

• __STDC__ – bool for whether compiler is C89-compliant
• __STDC_VERSION__ – 199901L >= if C99-compliant
• __STDC_IEC_559__ – bool for IEEE-754 compliance

Stdlib survey

• stdlib.h: malloc(), free(), array sorting, binary search, str->num conversion, random numbers
• stddef.h: defines NULL, size_t
• string.h: also includes general array/memory stuff
• math.h, time.h: speak for themselves
• errno.h: defines errno global var
• ctype.h: ASCII character classification
• fenv.h: controls floating point rounding mode, etc [C99 only]
• limits.h: limits of integer types
• float.h: describes properties of float representation
• See also my summary of the essential parts of the stdlib

GCC options

• -o exec_name (instead of a.out)
• -Idir_name:other_dir_name (places to also look for headers)
• -fsyntax-only (just check syntax)
• -ansi (use C89)
• -std=c99 (use C99)
• -Wall (warn about a bunch of stuff)
• -pedantic (adhere pedantically to standard)
• -Wextra (warn about strange/pointless code)
• -g (add debug info)
• -pg (add profiling hooks)