feat: Add snprintf

This patch adds snprintf. The second parameter "size" is expected to
accept only zero or positive integer, otherwise as C11 specification
states, it would be undefined behavior.

Co-authored-by: Jim Hsu <[email protected]>

Author: Jim Hsu

lib/c.c

@@ -288,60 +288,63 @@ int __format(char *buffer,
     return bi;
 }
 
-void printf(char *str, ...)
+int __format_to_buf(char *buffer, char *format, int *var_args, int size)
 {
-    int *var_args = &str + 4;
-    char buffer[200];
     int si = 0, bi = 0, pi = 0;
 
-    while (str[si]) {
-        if (str[si] != '%') {
-            buffer[bi] = str[si];
+    if (size == 0)
+        return 0;
+
+    while (format[si]) {
+        if (bi >= size - 1) {
+            break;
+        } else if (format[si] != '%') {
+            buffer[bi] = format[si];
             bi++;
             si++;
         } else {
             int w = 0, zp = 0, pp = 0;
 
             si++;
-            if (str[si] == '#') {
+            if (format[si] == '#') {
                 pp = 1;
                 si++;
             }
-            if (str[si] == '0') {
+            if (format[si] == '0') {
                 zp = 1;
                 si++;
             }
-            if (str[si] >= '1' && str[si] <= '9') {
-                w = str[si] - '0';
+            if (format[si] >= '1' && format[si] <= '9') {
+                w = format[si] - '0';
                 si++;
-                while (str[si] >= '0' && str[si] <= '9') {
+                while (format[si] >= '0' && format[si] <= '9') {
                     w *= 10;
-                    w += str[si] - '0';
+                    w += format[si] - '0';
                     si++;
                 }
             }
-            if (str[si] == 's') {
+            if (format[si] == 's') {
                 /* append param pi as string */
                 int l = strlen(var_args[pi]);
                 strcpy(buffer + bi, var_args[pi]);
                 bi += l;
-            } else if (str[si] == 'c') {
+            } else if (format[si] == 'c') {
                 /* append param pi as char */
                 buffer[bi] = var_args[pi];
                 bi += 1;
-            } else if (str[si] == 'o') {
+            } else if (format[si] == 'o') {
                 /* append param as octal */
                 int v = var_args[pi];
                 bi += __format(buffer + bi, v, w, zp, 8, pp);
-            } else if (str[si] == 'd') {
+            } else if (format[si] == 'd') {
                 /* append param as decimal */
                 int v = var_args[pi];
                 bi += __format(buffer + bi, v, w, zp, 10, 0);
-            } else if (str[si] == 'x') {
+            } else if (format[si] == 'x') {
                 /* append param as hex */
                 int v = var_args[pi];
                 bi += __format(buffer + bi, v, w, zp, 16, pp);
-            } else if (str[si] == '%') {
+            } else if (format[si] == '%') {
                 /* append literal '%' character */
                 buffer[bi] = '%';
                 bi++;
@@ -352,71 +355,28 @@ void printf(char *str, ...)
             si++;
         }
     }
-    buffer[bi] = 0;
-    __syscall(__syscall_write, 1, buffer, bi);
+
+    int len = size - 1 > bi ? bi : size - 1;
+    buffer[len] = 0;
+    return len;
 }
 
-void sprintf(char *buffer, char *str, ...)
+int printf(char *str, ...)
 {
-    int *var_args = &str + 4;
-    int si = 0, bi = 0, pi = 0;
+    char buffer[200];
+    int len = __format_to_buf(buffer, str, &str + 4, 0x7fffffff);
+    __syscall(__syscall_write, 1, buffer, len);
+    return len;
+}
 
-    while (str[si]) {
-        if (str[si] != '%') {
-            buffer[bi] = str[si];
-            bi++;
-            si++;
-        } else {
-            int w = 0, zp = 0, pp = 0;
+int sprintf(char *buffer, char *str, ...)
+{
+    return __format_to_buf(buffer, str, &str + 4, 0x7fffffff);
+}
 
-            si++;
-            if (str[si] == '#') {
-                pp = 1;
-                si++;
-            }
-            if (str[si] == '0') {
-                zp = 1;
-                si++;
-            }
-            if (str[si] >= '1' && str[si] <= '9') {
-                w = str[si] - '0';
-                si++;
-                if (str[si] >= '0' && str[si] <= '9') {
-                    w *= 10;
-                    w += str[si] - '0';
-                    si++;
-                }
-            }
-            switch (str[si]) {
-            case 37: /* % */
-                buffer[bi++] = '%';
-                si++;
-                continue;
-            case 99: /* c */
-                buffer[bi++] = var_args[pi];
-                break;
-            case 115: /* s */
-                strcpy(buffer + bi, var_args[pi]);
-                bi += strlen(var_args[pi]);
-                break;
-            case 111: /* o */
-                bi += __format(buffer + bi, var_args[pi], w, zp, 8, pp);
-                break;
-            case 100: /* d */
-                bi += __format(buffer + bi, var_args[pi], w, zp, 10, 0);
-                break;
-            case 120: /* x */
-                bi += __format(buffer + bi, var_args[pi], w, zp, 16, pp);
-                break;
-            default:
-                abort();
-                break;
-            }
-            pi++;
-            si++;
-        }
-    }
-    buffer[bi] = 0;
+int snprintf(char *buffer, int n, char *str, ...)
+{
+    return __format_to_buf(buffer, str, &str + 4, n);
 }
 
 int __free_all();

src/defs.h

@@ -17,17 +17,17 @@
 #define MAX_VAR_LEN 32
 #define MAX_TYPE_LEN 32
 #define MAX_PARAMS 8
-#define MAX_LOCALS 1500
+#define MAX_LOCALS 1600
 #define MAX_FIELDS 64
 #define MAX_FUNCS 512
 #define MAX_TYPES 64
-#define MAX_IR_INSTR 50000
+#define MAX_IR_INSTR 60000
 #define MAX_BB_PRED 128
 #define MAX_BB_DOM_SUCC 64
 #define MAX_BB_RDOM_SUCC 256
 #define MAX_GLOBAL_IR 256
 #define MAX_LABEL 4096
-#define MAX_SOURCE 327680
+#define MAX_SOURCE 524288
 #define MAX_CODE 262144
 #define MAX_DATA 262144
 #define MAX_SYMTAB 65536
@@ -39,7 +39,7 @@
 #define MAX_CASES 128
 #define MAX_NESTING 128
 #define MAX_OPERAND_STACK_SIZE 32
-#define MAX_ANALYSIS_STACK_SIZE 750
+#define MAX_ANALYSIS_STACK_SIZE 800
 
 /* Default capacities for common data structures */
 /* Default arena size is initialized with 256 KiB */

src/parser.c

@@ -3401,17 +3401,15 @@ void load_source_file(char *file)
         }
         if (!strncmp(buffer, "#include ", 9) && (buffer[9] == '"')) {
             char path[MAX_LINE_LEN];
-            int c = strlen(file) - 1;
+            int c = strlen(file) - 1, inclusion_path_len = strlen(buffer) - 11;
             while (c > 0 && file[c] != '/')
                 c--;
             if (c) {
                 /* prepend directory name */
-                strncpy(path, file, c + 1);
-                c++;
+                snprintf(path, c + 2, "%s", file);
             }
-            path[c] = 0;
-            buffer[strlen(buffer) - 2] = 0;
-            strcpy(path + c, buffer + 10);
+
+            snprintf(path + c + 1, inclusion_path_len, "%s", buffer + 10);
             load_source_file(path);
         } else {
             strcpy(SOURCE + source_idx, buffer);

tests/driver.sh

@@ -1611,4 +1611,57 @@ int main()
 }
 EOF
 
+# printf family, including truncation and zero size input
+try_output 11 "Hello World" << EOF
+int main() {
+    int written = printf("Hello World");
+    return written;
+}
+EOF
+
+try_output 11 "Hello World" << EOF
+int main() {
+    char buffer[50];
+    int written = sprintf(buffer, "Hello World");
+    printf("%s", buffer);
+    return written;
+}
+EOF
+
+try_output 16 "Hello World 1123" << EOF
+int main() {
+    char buffer[50];
+    int written = sprintf(buffer, "Hello %s %d", "World", 1123);
+    printf("%s", buffer);
+    return written;
+}
+EOF
+
+try_output 16 "Hello World 1123" << EOF
+int main() {
+    char buffer[50];
+    int written = snprintf(buffer, 50, "Hello %s %d", "World", 1123);
+    printf("%s", buffer);
+    return written;
+}
+EOF
+
+try_output 0 "" << EOF
+int main() {
+    char buffer[20];
+    int written = snprintf(buffer, 0, "Number: %d", -37);
+    printf("%s", buffer);
+    return written;
+}
+EOF
+
+try_output 9 "Number: -" << EOF
+int main() {
+    char buffer[10];
+    int written = snprintf(buffer, 10, "Number: %d", -37);
+    printf("%s", buffer);
+    return written;
+}
+EOF
+
 echo OK