Merged revisions 72487-72488,72879 via svnmerge from

svn+ssh://pythondev@svn.python.org/python/trunk

........
  r72487 | jeffrey.yasskin | 2009-05-08 17:51:06 -0400 (Fri, 08 May 2009) | 7 lines

  PyCode_NewEmpty:
  Most uses of PyCode_New found by http://www.google.com/codesearch?q=PyCode_New
  are trying to build an empty code object, usually to put it in a dummy frame
  object. This patch adds a PyCode_NewEmpty wrapper which lets the user specify
  just the filename, function name, and first line number, instead of also
  requiring lots of code internals.
........
  r72488 | jeffrey.yasskin | 2009-05-08 18:23:21 -0400 (Fri, 08 May 2009) | 13 lines

  Issue 5954, PyFrame_GetLineNumber:
  Most uses of PyCode_Addr2Line
  (http://www.google.com/codesearch?q=PyCode_Addr2Line) are just trying to get
  the line number of a specified frame, but there's no way to do that directly.
  Forcing people to go through the code object makes them know more about the
  guts of the interpreter than they should need.

  The remaining uses of PyCode_Addr2Line seem to be getting the line from a
  traceback (for example,
  http://www.google.com/codesearch/p?hl=en#u_9_nDrchrw/pygame-1.7.1release/src/base.c&q=PyCode_Addr2Line),
  which is replaced by the tb_lineno field.  So we may be able to deprecate
  PyCode_Addr2Line entirely for external use.
........
  r72879 | jeffrey.yasskin | 2009-05-23 19:23:01 -0400 (Sat, 23 May 2009) | 14 lines

  Issue #6042:
  lnotab-based tracing is very complicated and isn't documented very well.  There
  were at least 3 comment blocks purporting to document co_lnotab, and none did a
  very good job. This patch unifies them into Objects/lnotab_notes.txt which
  tries to completely capture the current state of affairs.

  I also discovered that we've attached 2 layers of patches to the basic tracing
  scheme. The first layer avoids jumping to instructions that don't start a line,
  to avoid problems in if statements and while loops.  The second layer
  discovered that jumps backward do need to trace at instructions that don't
  start a line, so it added extra lnotab entries for 'while' and 'for' loops, and
  added a special case for backward jumps within the same line. I replaced these
  patches by just treating forward and backward jumps differently.
........

1 files changed, 3 insertions, 51 deletions

diff --git a/Python/compile.c b/Python/compile.c
index 787dfe3..24975b6 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -1748,9 +1748,6 @@ compiler_for(struct compiler *c, stmt_ty s)
 	VISIT(c, expr, s->v.For.iter);
 	ADDOP(c, GET_ITER);
 	compiler_use_next_block(c, start);
-	/* for expressions must be traced on each iteration,
-	   so we need to set an extra line number. */
-	c->u->u_lineno_set = 0;
 	ADDOP_JREL(c, FOR_ITER, cleanup);
 	VISIT(c, expr, s->v.For.target);
 	VISIT_SEQ(c, stmt, s->v.For.body);
@@ -1796,9 +1793,6 @@ compiler_while(struct compiler *c, stmt_ty s)
 	if (!compiler_push_fblock(c, LOOP, loop))
 		return 0;
 	if (constant == -1) {
-		/* while expressions must be traced on each iteration,
-		   so we need to set an extra line number. */
-		c->u->u_lineno_set = 0;
 		VISIT(c, expr, s->v.While.test);
 		ADDOP_JABS(c, POP_JUMP_IF_FALSE, anchor);
 	}
@@ -3654,51 +3648,9 @@ blocksize(basicblock *b)
 	return size;
 }
 
-/* All about a_lnotab.
-
-c_lnotab is an array of unsigned bytes disguised as a Python string.
-It is used to map bytecode offsets to source code line #s (when needed
-for tracebacks).
-
-The array is conceptually a list of
-    (bytecode offset increment, line number increment)
-pairs.	The details are important and delicate, best illustrated by example:
-
-    byte code offset	source code line number
-	0		    1
-	6		    2
-       50		    7
-      350		  307
-      361		  308
-
-The first trick is that these numbers aren't stored, only the increments
-from one row to the next (this doesn't really work, but it's a start):
-
-    0, 1,  6, 1,  44, 5,  300, 300,  11, 1
-
-The second trick is that an unsigned byte can't hold negative values, or
-values larger than 255, so (a) there's a deep assumption that byte code
-offsets and their corresponding line #s both increase monotonically, and (b)
-if at least one column jumps by more than 255 from one row to the next, more
-than one pair is written to the table. In case #b, there's no way to know
-from looking at the table later how many were written.	That's the delicate
-part.  A user of c_lnotab desiring to find the source line number
-corresponding to a bytecode address A should do something like this
-
-    lineno = addr = 0
-    for addr_incr, line_incr in c_lnotab:
-	addr += addr_incr
-	if addr > A:
-	    return lineno
-	lineno += line_incr
-
-In order for this to work, when the addr field increments by more than 255,
-the line # increment in each pair generated must be 0 until the remaining addr
-increment is < 256.  So, in the example above, assemble_lnotab (it used
-to be called com_set_lineno) should not (as was actually done until 2.2)
-expand 300, 300 to 255, 255, 45, 45, 
-	    but to 255,	  0, 45, 255, 0, 45.
-*/
+/* Appends a pair to the end of the line number table, a_lnotab, representing
+   the instruction's bytecode offset and line number.  See
+   Objects/lnotab_notes.txt for the description of the line number table. */
 
 static int
 assemble_lnotab(struct assembler *a, struct instr *i)