start with wc

build.sh

@@ -1,3 +1,11 @@
+assemble () {
+  FILE="$1"
+  PROGRAM_NAME="$2"
+
+  echo "Assembling $PROGRAM_NAME"
+  nasm -g -F dwarf -f elf64 "$FILE" -o "./target/$PROGRAM_NAME.o" || return
+}
+
 build () {
     FILE="$1"
     PROGRAM_NAME=$(basename "$FILE" ".asm")
@@ -7,8 +15,16 @@ build () {
         return
     fi
 
-    echo "Building $PROGRAM_NAME"
-    nasm -g -F dwarf -f elf64 "$FILE" -o "./target/$PROGRAM_NAME.o" && ld.lld "./target/$PROGRAM_NAME.o" -o "./target/$PROGRAM_NAME"
+
+    if [ "$PROGRAM_NAME" = "common" ]; then
+      # common does not need to be linked into an executable
+      return
+    fi
+
+    assemble "$FILE" "$PROGRAM_NAME"
+
+    echo "Linking $PROGRAM_NAME"
+    ld.lld "./target/$PROGRAM_NAME.o" "./target/common.o" -o "./target/$PROGRAM_NAME"
 }
 
 
@@ -21,6 +37,9 @@ if [ ! -d ./target ]; then
   mkdir ./target
 fi
 
+
+assemble "src/common.asm" "common"
+
 if [ "$#" -eq 0 ]; then
   for FILE in ./src/*.asm ; do
     build "$FILE"

src/common.asm

@@ -1,37 +1,4 @@
-          global    _start
-
-NUMBER EQU 0
-
-          section   .data
-buffer:   times 8 db 0
-
-
-          section   .text
-_start:
-          mov       rax, NUMBER
-          mov       rbx, buffer
-          call      itoa
-          cmp       rax, 0
-          jnz       error
-
-write_buffer:
-          mov       rax, 1          ; write
-          mov       rdi, 1          ; stdout
-          mov       rsi, buffer
-          mov       rdx, rbx        ; the length
-          syscall
-
-graceful_exit:
-          xor       rdi, rdi
-          jmp       exit
-
-error:
-          mov       rdi, 1
-exit:
-          mov       rax, 60
-          syscall
-
-
+          global     itoa
 
 ; itoa - converts an unsigned integer into its ascii representation
 ; inputs:
@@ -41,10 +8,12 @@ exit:
 ;   rax - 0: success, 1: error
 ;   rbx - the length
 
-MAX_SIZE EQU 100000
+MAX_SIZE EQU 1000000000
 START_DIVISOR EQU MAX_SIZE / 10
 ASCII_NUM EQU 48
 
+          section   .text
+
 itoa:
 ; r12: whether we are in the leading zeroes (bool)
 ; r11: buffer start

src/wc.asm

@@ -0,0 +1,21 @@
+          extern     itoa
+          global     _start
+
+          section   .data
+itoa_buf: times 100 db 0
+
+          section   .text
+_start:
+          mov       rax, 45354
+          mov       rbx, itoa_buf
+          call      itoa
+
+          mov       rdx, rbx
+          mov       rax, 1
+          mov       rdi, 1
+          mov       rsi, itoa_buf
+          syscall
+
+          mov       rax, 60
+          xor       rdi, rdi
+          syscall