more demo

demo/add.c

@@ -0,0 +1,9 @@
+int printf(const char format[], ...);
+int scanf(const char format[], ...);
+int putchar(int ch);
+
+
+int main() {
+    int a = 1;
+    return (a+(a+(a+(a+(a+(a+(a+(a+(a+(a+(a)))))))))));
+}

demo/lut.c

@@ -0,0 +1,47 @@
+int printf(const char format[], ...);
+int getchar();
+
+char string_table[65536];
+int string_offset;
+int string_lut[4096];
+int string_lut_size;
+
+int parse_string() {
+    int offset = string_offset;
+    int ch;
+    while ((ch = getchar()) != '"') {
+        if (ch == -1 || ch == '\n') {
+            printf("expecting '\"'\n");
+            return 1;
+        }
+        string_table[string_offset++] = ch;
+    }
+    string_table[string_offset++] = 0;
+    string_lut[string_lut_size] = offset;
+    return string_lut_size++;
+}
+
+
+int streq(const char* s1, const char* s2) {
+    while (*s1 && *s2 && *s1 == *s2) {
+        s1++;
+        s2++;
+    }
+    return *s1 == *s2;
+}
+
+void dump_string_table() {
+    printf(".data\n");
+    for (int i = 0; i < string_lut_size; ++i) {
+        char* id = string_table + string_lut[i];
+        printf(".LC%d: .string \"%s\", const: %d\n", 
+            i, id, streq(id, "const"));
+    }
+}
+
+int main() {
+    char ch;
+    while ((ch = getchar()) == '"') parse_string();
+    dump_string_table();
+    return 0;
+}

demo/parse.c

@@ -0,0 +1,19 @@
+int getchar();
+
+
+int is_digit(int ch) {
+    return '0' <= ch && ch <= '9';
+}
+
+int parse_int(int ch) {
+    int num = ch - '0';
+    while (is_digit(ch = getchar())) {
+        num = num * 10;
+        num = num + ch - '0';
+    }
+    return num;
+}
+
+int main() {
+    return parse_int(getchar());
+}

demo/strcmp.c

@@ -0,0 +1,17 @@
+int printf(const char* format, ...);
+
+int strcmp(const char* s1, const char* s2) {
+    while (*s1 && *s2 && *s1 == *s2) {
+        s1++;
+        s2++;
+    }
+    return *s1 - *s2;
+}
+
+int main() {
+    const char* s1 = "helloworld";
+    const char* s2 = "world";
+    printf("%d\n", strcmp(s1, s2));
+    printf("%d\n", strcmp(s1 + 5, s2));
+    return 0;
+}