This document discusses the C programming language and its compilation process. It covers preprocessor directives, compiling, assembling, linking, and makefiles. It also briefly mentions language features like function prototypes, inline functions, header files, and magic tricks used in the C implementation.

1. OSDC 2007
A Humbling Language
Rusty Russell

2. Time Better Spent
tcmalloc
●
http://goog-perftools.sourceforge.net/doc/tcmalloc.html
–
tdb
●
– ftp://ftp.samba.org/pub/unpacked/tdb
lguest
●
http://lguest.ozlabs.org
–

3. ABCDEFG
HIJKLM
NOPQRST
UVWXYZ

4. BCD G
LM
NOP RS
UVW Z

5. C
LM
NO S
VW Z

6. C
O S

7. C
O S

8. C
S

9. C
S

10. C

11. C

12. C

13. C: A Historic Language

14. http://www.thorstenkoerner.de/uploads/thompson_ritchie.jpg

15. +=
register
entry

16. foo.c

17. foo.c
preprocessor

18. foo.c
#define FOO 17
preprocessor

19. foo.c
#define FOO(x) (17*(x))
preprocessor

20. foo.c
#ifdef LINUX
...
#else
preprocessor
...
#endif

21. foo.c
#include quot;foo.hquot;
preprocessor

22. foo.c
#include quot;foo.hquot;
foo.h
preprocessor

23. foo.c
#include quot;foo.hquot;
foo.h
preprocessor
#include <stdio.h>

24. foo.c
#include quot;foo.hquot;
foo.h
preprocessor
#include <stdio.h>
stdio.h

25. foo.c
#include quot;foo.hquot;
foo.h
preprocessor
#include <stdio.h>
stdio.h
# include <features.h>
# include <stddef.h>
# include <bits/types.h>
#include <libio.h>
# include <stdarg.h>
#include <bits/stdio_lim.h>
#include <bits/sys_errlist.h>
# include <getopt.h>
# include <bits/stdio.h>
# include <bits/stdio2.h>
# include <bits/stdio-ldbl.h>

26. foo.c
preprocessor

27. foo.c
preprocessor

28. foo.c
preprocessor
foo.i

29. foo.c
preprocessor
compiler

30. foo.c
preprocessor
compiler

31. foo.c
preprocessor
compiler
foo.s

32. foo.c
preprocessor
compiler
assembler

33. foo.c bar.c baz.c
preprocessor
compiler
assembler

34. foo.c bar.c baz.c
preprocessor
compiler
assembler
linker

35. foo.c bar.c baz.c
preprocessor
compiler
assembler
linker
foobarbaz

36. foo.c bar.c baz.c
make
preprocessor
compiler
assembler
linker
foobarbaz

37. foo.c bar.c baz.c
make
preprocessor
compiler
ccache
assembler
linker
foobarbaz

38. foo.c bar.c baz.c
make
preprocessor
compiler
ccache
distcc
assembler
linker
foobarbaz

39. foo.c bar.c baz.c
make
preprocessor
ccontrol
compiler
ccache
distcc
assembler
linker
foobarbaz

40. foo.c bar.c baz.c
make gcc *.c
preprocessor
ccontrol
compiler
ccache
distcc
assembler
linker
foobarbaz

41. 1988

42. entry
void
const
volatile
enum
function prototypes

43. 1999

44. inline

45. foo.c bar.c baz.c
preprocessor
int
compiler foo(int x)...
assembler
linker
foobarbaz

46. foo.c bar.c baz.c
preprocessor
int
compiler foo(int x)...
assembler
linker
foobarbaz

47. foo.c bar.c baz.c
preprocessor foo.h
compiler
assembler
linker
foobarbaz

48. foo.c bar.c baz.c
preprocessor foo.h
inline int
foo(int x)...
compiler
assembler
linker
foobarbaz

49. WTF?

50. WTF?
This isn't a
scripting
language!

56. Images from Wikipedia

57. C

58. C
C

59. C
C
CC

60. C
ontrol

61. C
ycles

62. C
ore

63. C
ache

64. “Sell Me a C!”

65. The Magic

66. The Magic

68. struct list_head
{
struct list_head *next, *prev;
};

69. struct list_head
{
struct list_head *next, *prev;
};
struct thing
{
struct list_head elem;
...
};

70. void *kmalloc(size_t size,
gfp_t flags);

71. Just a little magic?

72. long f(struct foo *a, struct foo *b)
{
return b – a;
}

73. Magic to get closer to the machine...

74. struct elems
{
unsigned int num_elems;
struct elem[0];
};

75. #define memcpy(t, f, n)
(__builtin_constant_p(n) ?
__constant_memcpy((t),(f),(n)) :
__memcpy((t),(f),(n)))

76. Magic to strengthen language features...

77. DANGER!
Magic to strengthen language features...

78. #define new(type)
((type *)malloc(sizeof(type))

79. #define min(x,y) ({
typeof(x) _x = (x);
typeof(y) _y = (y);
(void) (&_x == &_y);
_x < _y ? _x : _y; })

80. _Bool

81. #include <stdbool.h>

82. #include <stdbool.h>
#define bool _Bool

84. #define begin {
#define end }

86. talloc(context, type)

94. valgrind

96. C