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gcc/clang -S main.c -o main.s

int foo(void);

#include "foo.h"

int square(int i) { return i * i; }

int main() {
  int a = 5;
  int f = foo();
  return f + square(a);
}

int a = 5;

int    a    = 5  ;

error: expected ';' at end of declaration
    6 |   int a = 5 @3;
      |            ^
      |

error: expected ';' at end of declaration
    6 |   int a = 5 // Missing the ;
      |            ^
      |

int main() {
  // int a = 5;
  int f = foo();
  return f + square(a);
}

 error: use of undeclared identifier 'a'
    8 |   return f + square(a);
      |                     ^

int a = "hello";

error: incompatible pointer to integer conversion initializing 'int' with an expression of type 'char[6]' [-Wint-conversion]
    6 |   int a = "hello";
      |       ^   ~~~~~~~

clang main.c -S -emit-llvm -o main.ll`

; ModuleID = 'main.c'
source_filename = "main.c"
target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128-Fn32"
target triple = "arm64-apple-macosx14.0.0"

; Function Attrs: noinline nounwind optnone ssp uwtable(sync)
define i32 @square(i32 noundef %0) #0 {
  %2 = alloca i32, align 4
  store i32 %0, ptr %2, align 4
  %3 = load i32, ptr %2, align 4
  %4 = load i32, ptr %2, align 4
  %5 = mul nsw i32 %3, %4
  ret i32 %5
}

; Function Attrs: noinline nounwind optnone ssp uwtable(sync)
define i32 @main() #0 {
  %1 = alloca i32, align 4
  %2 = alloca i32, align 4
  %3 = alloca i32, align 4
  store i32 0, ptr %1, align 4
  store i32 5, ptr %2, align 4
  %4 = call i32 @foo()
  store i32 %4, ptr %3, align 4
  %5 = load i32, ptr %3, align 4
  %6 = load i32, ptr %2, align 4
  %7 = call i32 @square(i32 noundef %6)
  %8 = add nsw i32 %5, %7
  ret i32 %8
}

declare i32 @foo() #1

attributes #0 = {...}
attributes #1 = {...}
...
...

    .text
    .file   "main.c"
    .globl  square                          // -- Begin function square
    .p2align    2
    .type   square,@function
square:                                 // @square
    .cfi_startproc
// %bb.0:
    sub sp, sp, #16
    .cfi_def_cfa_offset 16
    str w0, [sp, #12]
    ldr w8, [sp, #12]
    ldr w9, [sp, #12]
    mul w0, w8, w9
    add sp, sp, #16
    .cfi_def_cfa_offset 0
    ret
.Lfunc_end0:
    .size   square, .Lfunc_end0-square
    .cfi_endproc
                                        // -- End function
    .globl  main                            // -- Begin function main
    .p2align    2
    .type   main,@function
main:                                   // @main
    .cfi_startproc
// %bb.0:
    sub sp, sp, #32
    .cfi_def_cfa_offset 32
    stp x29, x30, [sp, #16]             // 16-byte Folded Spill
    add x29, sp, #16
    .cfi_def_cfa w29, 16
    .cfi_offset w30, -8
    .cfi_offset w29, -16
    stur    wzr, [x29, #-4]
    mov w8, #5                          // =0x5
    str w8, [sp, #8]
    bl  foo
    str w0, [sp, #4]
    ldr w8, [sp, #4]
    str w8, [sp]                        // 4-byte Folded Spill
    ldr w0, [sp, #8]
    bl  square
    ldr w8, [sp]                        // 4-byte Folded Reload
    add w0, w8, w0
    .cfi_def_cfa wsp, 32
    ldp x29, x30, [sp, #16]             // 16-byte Folded Reload
    add sp, sp, #32
    .cfi_def_cfa_offset 0
    .cfi_restore w30
    .cfi_restore w29
    ret
.Lfunc_end1:
    .size   main, .Lfunc_end1-main
    .cfi_endproc
                                        // -- End function
    .ident  "Ubuntu clang version 18.1.3 (1ubuntu1)"
    .section    ".note.GNU-stack","",@progbits
    .addrsig
    .addrsig_sym square
    .addrsig_sym foo

    .section    __TEXT,__text,regular,pure_instructions
    .build_version macos, 14, 0 sdk_version 14, 4
    .globl  _square                         ; -- Begin function square
    .p2align    2
_square:                                ; @square
    .cfi_startproc
; %bb.0:
    sub sp, sp, #16
    .cfi_def_cfa_offset 16
    str w0, [sp, #12]
    ldr w8, [sp, #12]
    ldr w9, [sp, #12]
    mul w0, w8, w9
    add sp, sp, #16
    ret
    .cfi_endproc
                                        ; -- End function
    .globl  _main                           ; -- Begin function main
    .p2align    2
_main:                                  ; @main
    .cfi_startproc
; %bb.0:
    sub sp, sp, #32
    stp x29, x30, [sp, #16]             ; 16-byte Folded Spill
    add x29, sp, #16
    .cfi_def_cfa w29, 16
    .cfi_offset w30, -8
    .cfi_offset w29, -16
    stur    wzr, [x29, #-4]
    mov w8, #5                          ; =0x5
    str w8, [sp, #8]
    bl  _foo
    str w0, [sp, #4]
    ldr w8, [sp, #4]
    str w8, [sp]                        ; 4-byte Folded Spill
    ldr w0, [sp, #8]
    bl  _square
    ldr w8, [sp]                        ; 4-byte Folded Reload
    add w0, w8, w0
    ldp x29, x30, [sp, #16]             ; 16-byte Folded Reload
    add sp, sp, #32
    ret
    .cfi_endproc
                                        ; -- End function
.subsections_via_symbols