GCC

Environment Variables

 
export C_INCLUDE_PATH=/opt/gdbm-1.8.3/include
export CPLUS_INCLUDE_PATH=/opt/gdbm-1.8.3/include
export LIBRARY_PATH=/opt/gdbm-1.8.3/lib
 

Include Path Search order

* Command line options (-I) from left to right
* Env variables (C_INCLUDE_PATH, CPLUS_INCLUDE_PATH)
* Standard default directories
- /usr/local/include
- /usr/include

Library Path Search order

* Command line options (-L) from left to right
* Env variables (LIBRARY_PATH)
* Standard default directories
- /usr/local/lib
- /usr/lib

Extended Search Path

* Multiple -I or -L entries. For example, -I. -I/opt/gdbm-1.8.3/include -I/net/include -L. -L/opt/gdbm-1.8.3/lib -L/net/lib .....
* Use colon as separator in env variables. For example,
C_INCLUDE_PATH=.:/opt/gdbm-1.8.3/include:/net/include
LIBRARY_PATH=.:/opt/gdbm-1.8.3/lib:/net/lib

Shared Library Path

LD_LIBRARY_PATH=/opt/gdbm-1.8.3/lib:/opt/gtk-1.4/lib
export LD_LIBRARY_PATH

ANSI/ISO Compliance

# Use -ansi
gcc -Wall -ansi pi.c

# Use -pedantic AND -ansi for strict ANSI/ISO compliance
gcc -Wall -ansi -pedantic gnuarray.c

Other Standards

-std=c89 or -std=iso9899:1990
-std=iso9899:199409
-std=c99 or -std=iso9899:1999

Recommended warning options

gcc -ansi -pedantic -Wall -W -Wconversion -Wshadow -Wcast-qual -Wwrite-strings

C Preprocessor (CPP)

* Expands macros before source files are compiled.
* Preprocess without compiling: -save-temps

 
# Use -E options
gcc -E hello.c
 
# Use -save-temps options
gcc -c -save-temps hello.c
 

Define macros

 
#ifdef TEST
  printf ("Test mode\n");
#endif
 

* Compile with gcc -Wall -DTEST dtest.c -o dtest will print "Test mode".
* Define in source files or header files

#define TEST "Hello, World!"

* Print predefined macros:

cpp -dM /dev/null

* Macro with values

 
printf ("Value of NUM is %d\n", NUM);
gcc -Wall -DNUM=100 dtestval.c
 

Debugging Core Dump

 
# Compile with -g option
gcc -Wall -g null.c -o null
 
# Set core dump file limit
ulimit -c unlimited
 
# Use gdb
gdb null core
(gdb) backtrace
(gdb) break main
(gdb) run
(gdb) step
(gdb) set variable p = malloc(sizeof(int))
(gdb) set variable *p = 255
(gdb) step
(gdb) step
(gdb) finish
(gdb) continue
 

Profiling

* Compile and link with -pg option

 
gcc -Wall -c -pg collatz.c
gcc -Wall -pg collatz.o
 

* Execute

 
./a.out
 

* Profile

 
gprof a.out
 

Compile C++

 
g++ -Wall hello.cc -o hello
 
# Compile for a specific CPU. Not portable!
g++ -Wall -march=pentium4 hello.cc -o hello
 

Debug/Kill a Hanged Program

 
# Compile with -g option
gcc -Wall -g loop.c
 
# Run it
./a.out
 
# Find pid
ps -x
 
# Attach gdb
gdb a.out
(gdb) attach 27189
(gdb) kill
Kill the program being debugged? (y or n) y
(gdb)
 

Create a Library with GNU Archiver

 
# Compile. No link (-c)
gcc -Wall -c hello_fn.c
gcc -Wall -c hello_fn.c
 
# Archive. Create and replace (cr)
ar cr libhello.a hello_fn.o bye_fn.o
 
# List content
ar t libhello.a
 
# Use lib
gcc -Wall hellolib.c libhello.a -o hellolib
# or -L. (include current dir) -lhello (shortcut library link option)
gcc -L. hellolib.c -lhello -o hellolib
 

C++ Standard Library Template

* libstdc++

Providing Own Template

* Follow "Inclusion Compilation Model": place template definition in header files.

How Compiler Works

Overview

* Preprocessing: expands macros

 
cpp hello.c > hello.i
 

* Compilation: source code to assembly code

 
gcc -Wall -S hello.i
 

* Assembly: assembly code to machine code

 
as hello.s -o hello.o
 

* Linking: create final executable

 
ld
  -dynamic-linker \
  /lib/ld-linux.so.2 \
  /usr/lib/crt1.o \
  /usr/lib/crti.o \
  /usr/lib/gcc-lib/i686/3.3.1/crtbegin.o \
  -L/usr/lib/gcc-lib/i686/3.3.1 \
  hello.o \
  -lgcc \
  -lgcc_eh \
  -lc \
  -lgcc \
  -lgcc_eh \
  /usr/lib/gcc-lib/i686/3.3.1/crtend.o \
  /usr/lib/crtn.o
 

Examine Compiled Files

* file

$ file a.out
a.out: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), for GNU/Linux 2.6.9, dynamically linked (uses shared libs), for GNU/Linux 2.6.9, not stripped

Examine Symbol Table

* nm
- T: defined
- U: undefined

Finding Dynamically Linked Libraries

* ldd

 ldd hello
        linux-gate.so.1 =>  (0x00362000)
        libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x00169000)
        libm.so.6 => /lib/libm.so.6 (0x0077c000)
        libgcc_s.so.1 => /lib/libgcc_s.so.1 (0x00101000)
        libc.so.6 => /lib/libc.so.6 (0x0063a000)
        /lib/ld-linux.so.2 (0x0061d000)

References

* http://www.network-theory.co.uk/gcc/intro/

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DIB

Overview

• Device independent bitmap
  • Can be moved from device to device (hence device independent)
• Normally transported in
  • metafiles
  • bmp files
  • clipboard (CF_DIB data format)
• Contains
  • bits
  • header 
    • describes the format of the bits
      • color format (color table)
      • size of the bitmap
• Supports
  • 1-bit, 4-bit, 8-bit
    • pixels are defined by indexes into color table
  • 24-bit
    • 1 byte each for red, green, and blue
• DIB functions
  • GetDIBits
  • SetDIBits
  • CreateDIBBitmap
  • SetDIBitsToDevice
  • StretchDIBits
  • CreateDIBPatternBrush

DIB Header

• Consists two adjoioning parts
  • header
  • color table
• Combined into the BITMAPINFO structure
  • biSize
  • biWidth
  • biHeight
  • biPlanes
    • Should always be 1
  • biBitCount
    • Color resolution in bits per pixel.
    • Allowed are 1, 4, 8, and 24
  • biCompression
    • Type of compression
    • Can be
      • BI_RGB
      • BI_RLE4
      • BI_RLE8
  • biSizeImage
    • Size of the bitmap proper in bytes
  •  biXPelsPerMeter
  • biYPelsPerMeter
  • biClrUsed
  • biClrImportant 

OS2 Style DIB

• A DIB file has
  • A file header
    
// 14 bytes since each WORD is 2 bytes and DWORD is 4
typedef struct tagBITMAPFILEHEADER // bmfh
{
  WORD bfType ; // signature word "BM" or 0x4D42
  DWORD bfSize ; // entire size of file
  WORD bfReserved1 ; // must be zero
  WORD bfReserved2 ; // must be zero
  DWORD bfOffsetBits ; // offset in file of DIB pixel bits
}
BITMAPFILEHEADER, * PBITMAPFILEHEADER ;

  • An information header
    
typedef struct tagBITMAPCOREHEADER // bmch
{
  DWORD bcSize ; // size of the structure = 12
  WORD bcWidth ; // width of image in pixels
  WORD bcHeight ; // height of image in pixels
  WORD bcPlanes ; // = 1
  WORD bcBitCount ; // bits per pixel (1, 4, 8, or 24)
}
BITMAPCOREHEADER, * PBITMAPCOREHEADER ;// Also defined in WINGDI.H
typedef struct tagBITMAPCOREINFO // bmci
{
  BITMAPCOREHEADER bmciHeader ; // core-header structure
  RGBTRIPLE bmciColors[1] ; // color table array
// Always 2, 16, or 256 RGBTRIPLE structures depending on bits per pixel
// Allocate PBITMAPCOREINFO for an 8-bit DIB
// pbmci = malloc (sizeof (BITMAPCOREINFO) + 255 * sizeof (RGBTRIPLE)) ;
}
BITMAPCOREINFO, * PBITMAPCOREINFO ;
  • An RGB color table (but not always. not with 24 bit/pixel DIB)
    • An array of 3 byte RGBTRIPLE structures
      
typedef struct tagRGBTRIPLE // rgbt
{
  BYTE rgbtBlue ; // blue level
  BYTE rgbtGreen ; // green level
  BYTE rgbtRed ; // red level
}
RGBTRIPLE ;

  • The bitmap pixel bits
• A in memory DIB has exactly as DIB file minus file header

http://support.microsoft.com/kb/q81498/

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Component Object Model (COM)

History

• VB cusotm controls
  • Dlls that expose properties and events
• VBX (VB extenstion) (1991) 
  • Based on 16 bit architecture
  • Allow VB to access components written in C and C++
• OLE1.0 (1991)
  • Deal with compound documents
  • Not popular
• OLE2.0 (1993)
  • Synonym to OLE
  • Built on COM

Architecture

• Binary standard to allow coomponents to interact with each other as objects
  • Not a programming language
• Exposes functionalities via interfaces

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OLE and ActiveX

Overview 

• ActiveX must
  • Communicate with its container using IUnknown COM interface 
  • Be able to create its own registries
• All OLEs are ActiveX but not the other way around 

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