py: Fix up source-line calculation.

Should address issue #475.

py/emitbc.c

@@ -79,15 +79,18 @@ STATIC void emit_write_code_info_qstr(emit_t* emit, qstr qstr) {
     c[3] = (qstr >> 24) & 0xff;
 }
 
+#if MICROPY_ENABLE_SOURCE_LINE
 STATIC void emit_write_code_info_bytes_lines(emit_t* emit, uint bytes_to_skip, uint lines_to_skip) {
-    for (; bytes_to_skip > 31; bytes_to_skip -= 31) {
-        *emit_get_cur_to_write_code_info(emit, 1) = 31;
-    }
-    for (; lines_to_skip > 7; lines_to_skip -= 7) {
-        *emit_get_cur_to_write_code_info(emit, 1) = 7 << 5;
+    assert(bytes_to_skip > 0 || lines_to_skip > 0);
+    while (bytes_to_skip > 0 || lines_to_skip > 0) {
+        uint b = MIN(bytes_to_skip, 31);
+        uint l = MIN(lines_to_skip, 7);
+        bytes_to_skip -= b;
+        lines_to_skip -= l;
+        *emit_get_cur_to_write_code_info(emit, 1) = b | (l << 5);
     }
-    *emit_get_cur_to_write_code_info(emit, 1) = bytes_to_skip | (lines_to_skip << 5);
 }
+#endif
 
 // all functions must go through this one to emit byte code
 STATIC byte* emit_get_cur_to_write_byte_code(emit_t* emit, int num_bytes_to_write) {
@@ -285,7 +288,7 @@ STATIC void emit_bc_end_pass(emit_t *emit) {
         printf("ERROR: stack size not back to zero; got %d\n", emit->stack_size);
     }
 
-    emit_write_code_info_bytes_lines(emit, 0, 0); // end of line number info
+    *emit_get_cur_to_write_code_info(emit, 1) = 0; // end of line number info
     emit_align_code_info_to_machine_word(emit); // align so that following byte_code is aligned
 
     if (emit->pass == PASS_2) {

py/showbc.c

@@ -33,6 +33,7 @@ void mp_byte_code_print(const byte *ip, int len) {
 
     // get code info size
     machine_uint_t code_info_size = ip[0] | (ip[1] << 8) | (ip[2] << 16) | (ip[3] << 24);
+    const byte *code_info = ip;
     ip += code_info_size;
 
     // bytecode prelude: state size and exception stack size; 16 bit uints
@@ -56,6 +57,21 @@ void mp_byte_code_print(const byte *ip, int len) {
         ip_start = ip;
     }
 
+    // print out line number info
+    {
+        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);
+        printf("File %s, block %s\n", qstr_str(source_file), qstr_str(block_name));
+        machine_int_t bc = (code_info + code_info_size) - ip;
+        machine_uint_t source_line = 1;
+        printf("  bc=" INT_FMT " line=" UINT_FMT "\n", bc, source_line);
+        for (const byte* ci = code_info + 12; *ci; ci++) {
+            bc += *ci & 31;
+            source_line += *ci >> 5;
+            printf("  bc=" INT_FMT " line=" UINT_FMT "\n", bc, source_line);
+        }
+    }
+
     machine_uint_t unum;
     qstr qstr;
     while (ip - ip_start < len) {

stmhal/mpconfigport.h

@@ -7,6 +7,7 @@
 #define MICROPY_ENABLE_GC           (1)
 #define MICROPY_ENABLE_FINALISER    (1)
 #define MICROPY_ENABLE_REPL_HELPERS (1)
+#define MICROPY_ENABLE_SOURCE_LINE  (1)
 #define MICROPY_LONGINT_IMPL        (MICROPY_LONGINT_IMPL_MPZ)
 #define MICROPY_FLOAT_IMPL          (MICROPY_FLOAT_IMPL_FLOAT)
 #define MICROPY_PATH_MAX            (128)