py: Fix line number printing for file with 1 line.

With a file with 1 line (and an error on that line), used to show the
line as number 0.  Now shows it correctly as line number 1.

But, when line numbers are disabled, it now prints line number 1 for any
line that has an error (instead of 0 as previously).  This might end up
being confusing, but requires extra RAM and/or hack logic to make it
print something special in the case of no line numbers.

py/emitglue.c

@@ -107,7 +107,7 @@ void mp_emit_glue_assign_native(mp_raw_code_t *rc, mp_raw_code_kind_t kind, void
 
 #ifdef WRITE_CODE
     FILE *fp_write_code = fopen("out-code", "wb");
-    fwrite(fun_data, len, 1, fp_write_code);
+    fwrite(fun_data, fun_len, 1, fp_write_code);
     fclose(fp_write_code);
 #endif
 #endif

py/vm.c

@@ -925,33 +925,29 @@ exception_handler:
                 mp_uint_t code_info_size = code_info[0] | (code_info[1] << 8) | (code_info[2] << 16) | (code_info[3] << 24);
                 qstr source_file = code_info[4] | (code_info[5] << 8) | (code_info[6] << 16) | (code_info[7] << 24);
                 qstr block_name = code_info[8] | (code_info[9] << 8) | (code_info[10] << 16) | (code_info[11] << 24);
-                mp_uint_t source_line = 0;
                 mp_uint_t bc = code_state->ip - code_info - code_info_size;
                 //printf("find %lu %d %d\n", bc, code_info[12], code_info[13]);
-                const byte* ci = code_info + 12;
-                if (*ci) {
-                    source_line = 1;
-                    mp_uint_t c;
-                    while ((c = *ci)) {
-                        mp_uint_t b, l;
-                        if ((c & 0x80) == 0) {
-                            // 0b0LLBBBBB encoding
-                            b = c & 0x1f;
-                            l = c >> 5;
-                            ci += 1;
-                        } else {
-                            // 0b1LLLBBBB 0bLLLLLLLL encoding (l's LSB in second byte)
-                            b = c & 0xf;
-                            l = ((c << 4) & 0x700) | ci[1];
-                            ci += 2;
-                        }
-                        if (bc >= b) {
-                            bc -= b;
-                            source_line += l;
-                        } else {
-                            // found source line corresponding to bytecode offset
-                            break;
-                        }
+                mp_uint_t source_line = 1;
+                mp_uint_t c;
+                for (const byte *ci = code_info + 12; (c = *ci);) {
+                    mp_uint_t b, l;
+                    if ((c & 0x80) == 0) {
+                        // 0b0LLBBBBB encoding
+                        b = c & 0x1f;
+                        l = c >> 5;
+                        ci += 1;
+                    } else {
+                        // 0b1LLLBBBB 0bLLLLLLLL encoding (l's LSB in second byte)
+                        b = c & 0xf;
+                        l = ((c << 4) & 0x700) | ci[1];
+                        ci += 2;
+                    }
+                    if (bc >= b) {
+                        bc -= b;
+                        source_line += l;
+                    } else {
+                        // found source line corresponding to bytecode offset
+                        break;
                     }
                 }
                 mp_obj_exception_add_traceback(nlr.ret_val, source_file, source_line, block_name);