Fix for line events in the case:

  def f(a):
    if a:
      print 5
    else:
      pass

diff --git a/Python/compile.c b/Python/compile.c
index 328c57bb0fd9527ee2747d96c28e51f42518d760..7bbcd62e745b748f1bcccf8af9daf8901f0080f4 100644 (file)
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -629,7 +629,10 @@ struct compiling {
        int c_maxstacklevel;    /* Maximum stack level */
        int c_firstlineno;
        PyObject *c_lnotab;     /* Table mapping address to line number */
-       int c_last_addr, c_last_line, c_lnotab_next;
+       int c_last_addr;        /* last op addr seen and recorded in lnotab */
+       int c_last_line;        /* last line seen and recorded in lnotab */
+       int c_lnotab_next;      /* current length of lnotab */
+       int c_lnotab_last;      /* start of last lnotab record added */
        char *c_private;        /* for private name mangling */
        int c_tmpname;          /* temporary local name counter */
        int c_nested;           /* Is block nested funcdef or lamdef? */
@@ -848,6 +851,7 @@ com_init(struct compiling *c, const char *filename)
        c->c_last_addr = 0;
        c->c_last_line = 0;
        c->c_lnotab_next = 0;
+       c->c_lnotab_last = 0;
        c->c_tmpname = 0;
        c->c_nested = 0;
        c->c_closure = 0;
@@ -964,6 +968,7 @@ com_set_lineno(struct compiling *c, int lineno)
        else {
                int incr_addr = c->c_nexti - c->c_last_addr;
                int incr_line = lineno - c->c_last_line;
+               c->c_lnotab_last = c->c_lnotab_next;
                while (incr_addr > 255) {
                        com_add_lnotab(c, 255, 0);
                        incr_addr -= 255;
@@ -980,6 +985,27 @@ com_set_lineno(struct compiling *c, int lineno)
        }
 }
 
+static void
+com_strip_lnotab(struct compiling *c)
+{
+       /* strip the last lnotab entry if no opcode were emitted.
+        * This prevents a line number to be generated on a final
+        * pass, like in the following example:
+        *
+        *    if a:
+        *        print 5
+        *    else:
+        *        pass
+        *
+        * Without the fix, a line trace event would be generated
+        * on the pass even if a is true (because of the implicit
+        * return).
+        */
+       if (c->c_nexti == c->c_last_addr && c->c_lnotab_last > 0) {
+               c->c_lnotab_next = c->c_lnotab_last;
+       }
+}
+
 static void
 com_addoparg(struct compiling *c, int op, int arg)
 {
@@ -4167,6 +4193,7 @@ compile_funcdef(struct compiling *c, node *n)
        c->c_infunction = 1;
        com_node(c, CHILD(n, 4));
        c->c_infunction = 0;
+       com_strip_lnotab(c);
        com_addoparg(c, LOAD_CONST, com_addconst(c, Py_None));
        com_push(c, 1);
        com_addbyte(c, RETURN_VALUE);
@@ -4218,6 +4245,7 @@ compile_classdef(struct compiling *c, node *n)
        else
                (void) com_addconst(c, Py_None);
        com_node(c, ch);
+       com_strip_lnotab(c);
        com_addbyte(c, LOAD_LOCALS);
        com_push(c, 1);
        com_addbyte(c, RETURN_VALUE);
@@ -4237,6 +4265,7 @@ compile_node(struct compiling *c, node *n)
                n = CHILD(n, 0);
                if (TYPE(n) != NEWLINE)
                        com_node(c, n);
+               com_strip_lnotab(c);
                com_addoparg(c, LOAD_CONST, com_addconst(c, Py_None));
                com_push(c, 1);
                com_addbyte(c, RETURN_VALUE);
@@ -4246,6 +4275,7 @@ compile_node(struct compiling *c, node *n)
        
        case file_input: /* A whole file, or built-in function exec() */
                com_file_input(c, n);
+               com_strip_lnotab(c);
                com_addoparg(c, LOAD_CONST, com_addconst(c, Py_None));
                com_push(c, 1);
                com_addbyte(c, RETURN_VALUE);