Hi!
I implemented the compiler to and including chapter 138. I compared my code to the git hub version and all was conforming. When I run the test program, however, I get significantly different results to those in the recording:
test.c ->
int test()
{
int b = *a;
}
Compiler terminal output ->
section .data
section .text
global test
; test function
test:
push ebp
mov ebp, esp
sub esp, 18380445687218192
add esp, 18380445687218192
pop ebp
ret
section .rodata
everything compiled fine
Can you imagine what is going wrong? Particularly the HUGE number after add esp and sub esp.
I'm working under Windows with a version of gcc and VS Code.
Up to now, all successful compilations ran OK.
Thanks in advance
Steve Smith
Hey Stephen,
It sounds to me like you could of derefrenced a pointer or are pointing to the wrong memory address that is why the number seems so big. Put a breakpoint on the add esp and sub esp lines and examine the pointer your passing. Compare your code with mine using GIT rather than manual comparsion and the mistake will become more clear.
Your welcome please let me know if you have any trouble debugging the issue
Thanks
Hi Daniel,
I did some research on the internet and discovered that there is some discussion on the interpretation of format "%lld". Depending on the version of the gcc and the word-length of the system, this can work properly or not, particularly with 64 bit systems.
I first tried format "%d" which gave me the correct solution (16). But the argument to be output is "long long". I tried casting the argument to long long, which indeed delivered the correct value of 16. I presume this is a compiler bug affecting my version of gcc.
In future I will remember to cast the argument under similar circumstances.
Regards and thanks
Steve.
Learn to create your very own C compiler from scratch. In this course we develop a compiler that compiles a subset of the C Programming Language. By the time you finish all modules of this course you will be able to compile C programs that use pointers, structures, unions, arrays, functions, for loops, while loops. do while loops, if statements, switches and much more! This course includes all course modules!
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Module 2
In module 2 of this course we create a code generator that produces 32 bit Intel assembly language that can then be passed through an assembler to produce a program binary that we can run. We also in this module create a resolver system which is responsible for taking a complicated expression such as "a->b.c.e[50] = 50" and breaking it down into simple steps and rules that our code generator can then easily follow. This abstraction is essential to ensure that the code generator does not become over complex. With the use of a resolver system we can ensure the code base remains clean.
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In module 3 of this course we create a preprocessor and macro system. This preprocessor system allows us to include header files in our C programs and also use a variety of macro keywords such as "#define" "#ifdef" , "sizeof" and many more.
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Requirements
You must have a basic experience of assembly language.
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How to build a C compiler from scratch
Full understanding of stackframes and how assembly language is generared for a C source file
Complete Understanding of lexical analysis and parsing
Daniel McCarthy is a seasoned software engineer, boasting an impressive career spanning over 14 years in the industry. Holding a Master's Degree in Advanced Computer Science from Cardiff Metropolitan University, his broad spectrum of experience encompasses everything from web development to complex compiler and interpreter development.
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Questions (1)
Stephen Smith
1 year ago
Hi! I implemented the compiler to and including chapter 138. I compared my code to the git hub version and all was conforming. When I run the test program, however, I get significantly different results to those in the recording: test.c -> int test() { int b = *a; } Compiler terminal output -> section .data section .text global test ; test function test: push ebp mov ebp, esp sub esp, 18380445687218192 add esp, 18380445687218192 pop ebp ret section .rodata everything compiled fine Can you imagine what is going wrong? Particularly the HUGE number after add esp and sub esp. I'm working under Windows with a version of gcc and VS Code. Up to now, all successful compilations ran OK. Thanks in advance Steve Smith
Daniel McCarthy
1 year ago
Hey Stephen, It sounds to me like you could of derefrenced a pointer or are pointing to the wrong memory address that is why the number seems so big. Put a breakpoint on the add esp and sub esp lines and examine the pointer your passing. Compare your code with mine using GIT rather than manual comparsion and the mistake will become more clear. Your welcome please let me know if you have any trouble debugging the issue Thanks
Stephen Smith
1 year ago
Hi Daniel, I did some research on the internet and discovered that there is some discussion on the interpretation of format "%lld". Depending on the version of the gcc and the word-length of the system, this can work properly or not, particularly with 64 bit systems. I first tried format "%d" which gave me the correct solution (16). But the argument to be output is "long long". I tried casting the argument to long long, which indeed delivered the correct value of 16. I presume this is a compiler bug affecting my version of gcc. In future I will remember to cast the argument under similar circumstances. Regards and thanks Steve.
Daniel McCarthy
1 year ago
No worries let me know if you have any more questions Thanks