This project is excellent! I learn a lot from it. But I am curious why not generate intermediate code in your project? Will it look a little "incomplete" ?

For example, the global symbol table has a max number of entries, I've been implementing everything dynamically and reallocing as necessary, however I am worried that I have missed some important reason for statically allocating memory.

Hello, I am a developer from China. Now, i am following your project to study. I like your project very much. Excuse me, can I translate and repost your project to my blog. Looking forward to your reply. Thanks !

Firstly, thank you for sharing this great compiler writing jounery, I'm rather interested!

I'm in chapter 4 (generating assembly code), and trying to follow the code.

Here's the out assembly codes (saved in file "out.s"):

	.text
LC0:
	.string	"%d\n"
_printint:
	pushq	%rbp
	movq	%rsp, %rbp
	subq	$16, %rsp
	movl	%edi, -4(%rbp)
	movl	-4(%rbp), %eax
	movl	%eax, %esi
	leaq	LC0(%rip), %rdi
	movl	$0, %eax
	call	[email protected]
	nop
	leave
	ret

	.globl	_main
_main:
	pushq	%rbp
	movq	%rsp, %rbp
	movq	$2, %r8
	movq	$3, %r9
	movq	$5, %r10
	imulq	%r9, %r10
	addq	%r8, %r10
	movq	$8, %r8
	movq	$3, %r9
	movq	%r8,%rax
	cqo
	idivq	%r9
	movq	%rax,%r8
	subq	%r8, %r10
	movq	%r10, %rdi
	call	_printint
	movl	$0, %eax
	popq	%rbp
	ret

When running it with

cc -o out out.s

, it complained with

out.s:13:2: error: unsupported symbol modifier in branch relocation
 call [email protected]
 ^

How is the error happened and how to fix it?

Thanks in advance!

PS:

1. I am using macOS Catalina 10.15.2
2. cc version is

Apple clang version 11.0.0 (clang-1100.0.33.17)
Target: x86_64-apple-darwin19.2.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin

3. The souce codes are compiled with cc -o comp1 -g cg.c expr.c gen.c main.c scan.c tree.c

This is probably a problem with my system. Starting from 05_Statements I'm getting the error:

data.h:10:9: error: unknown type name ‘FILE’
   10 | extern_ FILE *Infile;                   // Input and output files
      |         ^~~~
data.h:11:9: error: unknown type name ‘FILE’
   11 | extern_ FILE *Outfile;
      |         ^~~~
data.h:13:19: error: ‘TEXTLEN’ undeclared here (not in a function)
   13 | extern_ char Text[TEXTLEN + 1];         // Last identifier scanned
      |                   ^~~~~~~
data.h:14:30: error: ‘NSYMBOLS’ undeclared here (not in a function)
   14 | extern_ struct symtable Gsym[NSYMBOLS]; // Global symbol table

Can anyone point me to the right direction. Thank you.

In the file cg.c at the line 176 you defined the following array for the inverted jump instructions:

// List of inverted jump instructions,
// in AST order: A_EQ, A_NE, A_LT, A_GT, A_LE, A_GE
static char *invcmplist[] = { "jne", "je", "jge", "jle", "jg", "jl" };

I think you inverted the jump instructions for greater/less than and greater/less equal.

In your code A_LT defines his inverse as "jge" and A_LE as "jg" and the same is with A_GT and A_GE which are respectively defined as "jle" and "jl".

Looking on various documentation online you can find that JL is defined as Jump short if Less and JLE as Jump short if Less or Equal. The same applies for the greater than/equal jumps, JG and JGE.

This means you defined the inverse for A_LT (less than) the jump if less or equal than and for A_LE (less equal) the jump if less than. As mentioned above the same error is done for the greater than/equal jumps.

The array should then be corrected as following:

// List of inverted jump instructions,
// in AST order: A_EQ, A_NE, A_LT, A_GT, A_LE, A_GE
static char *invcmplist[] = { "jne", "je", "jg", "jl", "jge", "jle" };

I've looked through all the parts of the tutorial and the error is still present in the last part (62 Cleanup).

There is a small typo in 06_Variables/misc.c, 07_Comparisons/misc.c, 08_If_Statements/misc.c, 09_While_Loops/misc.c, 10_For_Loops/misc.c, 11_Functions_pt1/misc.c, 12_Types_pt1/misc.c, 13_Functions_pt2/misc.c, 14_ARM_Platform/misc.c, 15_Pointers_pt1/misc.c, 16_Global_Vars/Readme.md, 16_Global_Vars/misc.c, 17_Scaling_Offsets/misc.c, 18_Lvalues_Revisited/misc.c, 19_Arrays_pt1/misc.c, 20_Char_Str_Literals/misc.c, 21_More_Operators/misc.c, 23_Local_Variables/misc.c, 24_Function_Params/misc.c, 25_Function_Arguments/misc.c, 26_Prototypes/misc.c, 27_Testing_Errors/misc.c, 28_Runtime_Flags/misc.c, 29_Refactoring/misc.c, 30_Design_Composites/Readme.md, 30_Design_Composites/misc.c, 31_Struct_Declarations/misc.c, 32_Struct_Access_pt1/Readme.md, 32_Struct_Access_pt1/expr.c, 32_Struct_Access_pt1/misc.c, 33_Unions/expr.c, 33_Unions/misc.c, 34_Enums_and_Typedefs/expr.c, 34_Enums_and_Typedefs/misc.c, 35_Preprocessor/expr.c, 35_Preprocessor/misc.c, 36_Break_Continue/expr.c, 36_Break_Continue/misc.c, 37_Switch/expr.c, 37_Switch/misc.c, 38_Dangling_Else/expr.c, 38_Dangling_Else/misc.c, 39_Var_Initialisation_pt1/expr.c, 39_Var_Initialisation_pt1/misc.c, 40_Var_Initialisation_pt2/expr.c, 40_Var_Initialisation_pt2/misc.c, 41_Local_Var_Init/expr.c, 41_Local_Var_Init/misc.c, 42_Casting/expr.c, 42_Casting/misc.c, 43_More_Operators/expr.c, 43_More_Operators/misc.c, 44_Fold_Optimisation/expr.c, 44_Fold_Optimisation/misc.c, 45_Globals_Again/expr.c, 45_Globals_Again/misc.c, 46_Void_Functions/expr.c, 46_Void_Functions/misc.c, 47_Sizeof/expr.c, 47_Sizeof/misc.c, 48_Static/expr.c, 48_Static/misc.c, 49_Ternary/expr.c, 49_Ternary/misc.c, 50_Mop_up_pt1/expr.c, 50_Mop_up_pt1/misc.c, 51_Arrays_pt2/expr.c, 51_Arrays_pt2/misc.c, 52_Pointers_pt2/Readme.md, 52_Pointers_pt2/misc.c, 53_Mop_up_pt2/misc.c, 54_Reg_Spills/misc.c, 56_Local_Arrays/misc.c, 57_Mop_up_pt3/misc.c, 58_Ptr_Increments/misc.c, 59_WDIW_pt1/misc.c, 60_TripleTest/misc.c, 62_Cleanup/misc.c.

Should read identifier rather than identifer.

the comparison operators have higher precedence than multiply and divide?

The expression '10 * 3 > 2 * 5' means '10 * 1 * 5= 15' ???

I don't agree with that. C Operator Precedence table is in descending precedence. That means comparison operators has lower precedence than mul and div.

  if (condition is true) 
    perform this first block of code
  else
    perform this other block of code

In readme, you write it like the following.

       perform the opposite comparison
       jump to L1 if true
       perform the first block of code
       jump to L2
L1:
       perform the other block of code
L2:

But there seems some wrong in jump to L1 if true. Do you mean jump to L1 if false ?

The variable breglist is declared here but not mentioned, and just shows up from nowhere in the doc.

https://github.com/DoctorWkt/acwj/blob/b11b269c71727297b367203eaed164364291db16/07_Comparisons/cg.c#L13

IMO it would better to mention the b-suffix somewhere before breglist appears in the journey.

Hi again 😺

You're probably aware of this already, but the scanner is too eager with scanning the '-' character as being part of an integer instead of an operand. For example:

#include <stdio.h>

int main() {
  printf("%d\n",1-1); // can't parse this, as scanner scans this as 2 consecutive T_INTLITs
  return (0);
}

Thanks,

I may be missing something here, but I think there's a typo in the code to check function parameters vs a prototype...

It looks as though the type for each argument is matched against the type of the function (Symtable[id].type), not the parameter in the prototype (which would be indexed by param_id)

We check both operands' type around = in modify_type() when the op is A_LOGOR or A_LOGAND, but it was misspelled to ltype when checking the right type. Also, I fix Now now to Not now in README file. fix #53

1. if (!inttype(ltype) && !ptrtype(rtype)) should be if (!inttype(rtype) && !ptrtype(rtype)) in modify_type().
2. Now now should be Not now in README file.

There is no need to call freestaticsyms() in do_compile() function. Because we already had clear_symtable() before we parse the source file. And clear_symtable() will clear all syms in Globhead chain.

after introducing array, code generator for arm seems not changed. And make armtest,input20 also fails with Segmentation fault. I guess function cgglobsym in cg_arm.c requires change.