gcc_gpp_comp_tut

# Include path:
The list of directories for header files is often referred to as the include path, a
# Library path
List of directories for libraries as the library search path or link path.
# Modifying these search paths when compiling:
# Where 'gdbm' library is within /opt/gdbm-1.8.3/lib
$ gcc -Wall -I/opt/gdbm-1.8.3/include -L/opt/gdbm-1.8.3/lib dbmain.c -lgdbm

#Environment variables to control the Include:
C_INCLUDE_PATH (for c) and CPLUS_INCLUDE_PATH (for cpp)

and the and Library path:
LIBRARY_PATH

and in order to control the search path for Shared library:
LD_LIBRARY_PATH

# Read excellent tutorial at: https://www3.ntu.edu.sg/home/ehchua/programming/cpp/gcc_make.html

#Useful stuff extracted from this tutorial:

#Knowing the default include-paths in your system used by the "GNU C Preprocessor": 
$ cpp -v

#Run the compilation in verbose mode (-v) to study the library-paths (-L) and libraries (-l) used in your system:
gcc -v -o hello.o hello.c

# 'nm' command to List Symbol Table of Object Files.
A 'T' in the second column indicates a function that is defined, while a 'U' 
indicates a function which is undefined and should be resolved by the linker.

# 'ldd' utility examines an executable and displays a list of the shared libraries that it needs.
$ ldd hello.o

#Another more thorough tutorial at:
https://www.linuxtopia.org/online_books/an_introduction_to_gcc/index.html

#
gcc -I /path/to/header_files1/ -I /path/to/header_files2/ main.c // here we add
\several folders with headers

###### Example of .c hello_world code :
#include <stdio.h>

int
main (void)
{
  printf ("Hello, world!\n");
  return 0;
}

Now we can compile (advisable activate all warnings:)
$ gcc -Wall hello.c -o hello
####
# Compiling multiple source files including the difference between using
# #include <hello.h> or using #include "hello.h"
# Read document at: https://www.linuxtopia.org/online_books/an_introduction_to_gcc/gccintro_11.html
####
# Linking a static library (in this case the Math library):

#include <math.h>
#include <stdio.h>

int
main (void)
{
  double x = sqrt (2.0);
  printf ("The square root of 2.0 is %f\n", x);
  return 0;
}

# Now, we can link by using:
gcc -Wall -lm calc.c -o calc # where -lm is used to specify the name of the library

###############]
# How can we list the contents of an *.a file (statis library)
ar t libhts.a
###############
# Debugging:

# If you want to compile a program with possibility of debugging it:
gcc -g main.c -o main

# Now, we can run the gdb debugger by doing:
gdb ./main

# We can create a Breakpoint by doing:
break main // where main is the name of your function

# And now if we enter:
run // it will go to the first line in function 'main'