cpsughrue / compiler Goto Github PK

This repository was created as an exercise to learn about compilers and is a work in progress. The compiler compiles math expressions to x86_64 assembly - Intel Syntax.

To build the math compiler and compile a simple math problem. Add the math problem to program.txt then run the build script: build.sh.

./build.sh

# Flags
#
#   -s, --scan-only: the compiler will scan the input file, print each token in 
#                    a human readable format, and exit. assembly is not generated
#                    and ./build_asm.sh will not be executed
#
#   -v, --verbose: the combiler will print log statements to the consol
#

# Example
cat program.txt
4 ^ 2 - 6 ^ 2 + 3

./build.sh
(((4^2)-(6^2))+3)
ASSEMBLY OUTPUT:  -17

The build script has three parts. Part one handles flags/arguments passed to build.sh by the user. Part two compiles the compiler with gcc and executes the binary. The path to program.txt is provided to the compiler as its first command line argument. During the code generation stage of execution the compiler will save the generated assembly to asm/program.asm. The third part calls asm/build_asm.sh which assembles, linkes, and executes the assembly. build_asm.sh uses nasm to assemble and ld to link the generated and prewritten x86_64 assembly. The prewritten assembly provides a built in way to print the result of the generated assembly.

• + <- addition
• - <- subtraction
• / <- floor division
• * <- multiplication
• ^ <- power
• % <- modulo

• No support for floating point numbers in input or output
  • 2.5 + 3 is an invalid expression
  • 5 / 2 will evaluate to 2 instead of 2.5
• Negative exponents evauate to 0 (related to the lack of floating point support)
  • 4 ^ -3 = 0
• Limited error detection
  • if there are multiple invalid tokens or multiple syntax errors the compiler will only identify the first one, print the error to the consol, and exit

• 3 + -2
• 6 / 3 + 2
• 6/3+2
• 4 ^ 2 - 6 ^ 2 + 3
• (8 + 2) * 834
• 4-2

In parenthesis are the versions used during development

• gcc (9.4.0)
• nasm (2.14.02)
• ld (2.34)