Lecture 6 CSCE 510 - CPP Implementation

• Ar assignment (write up in email soon) due Friday Sept 20
  • t implementation
  • build some "test" archives using the real ar
  • t; next ? maybe handle args
• Make from last handout
• Tsearch revisited
  • tsearch.c from man page
  • tsearch.ex.c
  • tsearchReclaim.c
• Static vs dynamic
• cc
  • c preprocessor
  • compiler (in old days two passes cc0, cc1)
  • optimization phase
  • assembler (as)
  • loader (ld)
  • man cc
    • /usr/ccs/bin(SUNs), /usr/lib/cmplrs(DEC)
    • /usr/lib/libc
    • a.out format in manual section 4 or 5?
  • options
    • -g include symbol table for debugging
    • -c
    • -i
    • -S
    • -E -P
    • -L dir
    • -I dir
    • -w
    • -p
    • -O -OO (optimizations on/off)
    • -o
    • -Dvar -Dvar=value
• CPP - C preprocessor
• Inclusion of header files
• Macro expansion
• conditional compilation
• line control
• CPP inline directives
  • start with # in column1
  • #include
  • #define
  • #undef
  • cond compilation: #ifdef, #ifndef, #else, #elseif, #endif
  • #line
• Simple Macros - no arguments

  #define name body
  
  Common errors
  #define name = body
  #define name body ;
  
  #define max(a,b) ((a < b) ? (b) :(a))
  

• stdio revisited
  • FILE structure
  • int fprintf (FILE *fp, const char *format [, arg ] ... )
  • int fscanf( stream, format [, pointer ] ... )
  • getc, putc, getchar, putchar, ungetc
• Macros in /usr/include/stdio.h

  #define getc(p)         (--(p)->_cnt>=0? *(p)->_ptr++&0377:_filbuf(p))
  #define getchar()       getc(stdin)
  #define putc(x,p) \
          (--(p)->_cnt>=0? \
                  ((int)(*(unsigned char *)(p)->_ptr++=(x))):\
                  _flsbuf((unsigned char)(x),p))
  #define putchar(x)      putc(x,stdout)
  #define feof(p)         (((p)->_flag&_IOEOF)!=0)
  #define ferror(p)       (((p)->_flag&_IOERR)!=0)
  #define fileno(p)       ((int)((p)->_file))
  
  

• getchar expansion
  • def
  • rescanning of text
  • implementation of rescanning of text
• Implementation Macros without arguments: char *name, *body
• Macros with arguments
• Implementation
  • ^Pn replacing parameter n in the body string
  • list of pointers to places to insert each argument
• Includes
  • read new file in to replace this line
  • nested includes imply that we need to save a stack of filenames and line numbers
• #include "file"
  1. look in "current directory" (the same as this file)
  2. then look in standard places
• #include
  1. look in standard places
• In either case with -Idir command line option look in dir before standrad places

[Readings:]

[Assignment:]

1. Dues Thursday midnight (if you attend class) Thursday 5:30 otherwise. Implement the "t" option of ar. It can be hardcoded at this point. Dropbox myar.c. Create a simple makefile with two targets: myar and clean.