Our ARM toolchain:

CC := $(GCC_ARM_BASE)arm-none-eabi-gcc
LD := $(GCC_ARM_BASE)arm-none-eabi-gcc
OBJCPY := $(GCC_ARM_BASE)arm-none-eabi-objcopy
OBJDUMP := $(GCC_ARM_BASE)arm-none-eabi-objdump
SIZE := $(GCC_ARM_BASE)arm-none-eabi-size
AR := $(GCC_ARM_BASE)arm-none-eabi-gcc-ar
GDB := $(GCC_ARM_BASE)arm-none-eabi-gdb
OPENOCD := openocd

Our X86 toolchain:

CC := $(COMPILER)
LD := $(COMPILER)
OBJCPY := objcopy
OBJDUMP := objdump
SIZE := size
AR := ar
GDB := gdb

What's a Toolchain?

In software, a toolchain is a set of programming tools that is used to perform a complex software development task or to create a software product, which is typically another computer program or a set of related programs.

A simple software development toolchain may consist of:

• compiler and 
• linker (which transform the source code into an executable program), 
• libraries (which provide interfaces to the operating system),
• debugger (which is used to test and debug created programs).

Our Toolchain: 

The GNU toolchain is a broad collection of programming tools produced by the GNU Project.

• GNU make: an automation tool for compilation and build
• GNU Compiler Collection (GCC): a suite of compilers for several programming languages
• GNU C Library (glibc): core C library including headers, libraries, and dynamic loader
• GNU Binutils: a suite of tools including linker, assembler and other tools
• GNU Bison: a parser generator, often used with the Flex lexical analyser
• GNU m4: an m4 macro processor
• GNU Debugger (GDB): a code debugging tool
• GNU build system (autotools): Autoconf, Automake and Libtool

Playing Around: 

Resources:

• four stages of compiling

Preprocessing:

This is where the macros expand, you can see the output of the preprocessing step, just run gcc with the -E option. 

#define hello_val 123

#define RETURN_HELLO_VAL(some_arg) \
do { \
  return some_arg; \
} while (0)

int main(void) {
  RETURN_HELLO_VAL(hello_val);
}

Running gcc hello.c -E returns something like:

(base) ➜  temp git:(master) ✗ gcc -E hello.c 
# 1 "hello.c"
# 1 "<built-in>" 1
# 1 "<built-in>" 3
# 362 "<built-in>" 3
# 1 "<command line>" 1
# 1 "<built-in>" 2
# 1 "hello.c" 2







int main(void) {
  do { return 123; } while (0);
}

beautiful.