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

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

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

* 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

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

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

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

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

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

* 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

#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

# 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

* Compile and link with -pg option

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

* Execute

./a.out

* Profile

gprof a.out

g++ -Wall hello.cc -o hello

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

# 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) 

# 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

* libstdc++

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

* 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

* 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

* nm
– T: defined
– U: undefined

* 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)

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