diff options
Diffstat (limited to 'Objects')
| -rw-r--r-- | Objects/codeobject.c | 11 | ||||
| -rw-r--r-- | Objects/frameobject.c | 2 | ||||
| -rw-r--r-- | Objects/lnotab_notes.txt | 37 |
3 files changed, 29 insertions, 21 deletions
diff --git a/Objects/codeobject.c b/Objects/codeobject.c index b0e34468a7..0f03dfe4b3 100644 --- a/Objects/codeobject.c +++ b/Objects/codeobject.c @@ -557,7 +557,8 @@ PyCode_Addr2Line(PyCodeObject *co, int addrq) addr += *p++; if (addr > addrq) break; - line += *p++; + line += (signed char)*p; + p++; } return line; } @@ -592,17 +593,19 @@ _PyCode_CheckLineNumber(PyCodeObject* co, int lasti, PyAddrPair *bounds) if (addr + *p > lasti) break; addr += *p++; - if (*p) + if ((signed char)*p) bounds->ap_lower = addr; - line += *p++; + line += (signed char)*p; + p++; --size; } if (size > 0) { while (--size >= 0) { addr += *p++; - if (*p++) + if ((signed char)*p) break; + p++; } bounds->ap_upper = addr; } diff --git a/Objects/frameobject.c b/Objects/frameobject.c index 425a9ee0f1..da2d2ed215 100644 --- a/Objects/frameobject.c +++ b/Objects/frameobject.c @@ -137,7 +137,7 @@ frame_setlineno(PyFrameObject *f, PyObject* p_new_lineno) new_lasti = -1; for (offset = 0; offset < lnotab_len; offset += 2) { addr += lnotab[offset]; - line += lnotab[offset+1]; + line += (signed char)lnotab[offset+1]; if (line >= new_lineno) { new_lasti = addr; new_lineno = line; diff --git a/Objects/lnotab_notes.txt b/Objects/lnotab_notes.txt index d247eddd6f..8af10db12e 100644 --- a/Objects/lnotab_notes.txt +++ b/Objects/lnotab_notes.txt @@ -12,42 +12,47 @@ pairs. The details are important and delicate, best illustrated by example: 0 1 6 2 50 7 - 350 307 - 361 308 + 350 207 + 361 208 Instead of storing these numbers literally, we compress the list by storing only -the increments from one row to the next. Conceptually, the stored list might +the difference from one row to the next. Conceptually, the stored list might look like: - 0, 1, 6, 1, 44, 5, 300, 300, 11, 1 + 0, 1, 6, 1, 44, 5, 300, 200, 11, 1 -The above doesn't really work, but it's a start. Note that an unsigned byte -can't hold negative values, or values larger than 255, and the above example -contains two such values. So we make two tweaks: +The above doesn't really work, but it's a start. An unsigned byte (byte code +offset)) can't hold negative values, or values larger than 255, a signed byte +(line number) can't hold values larger than 127 or less than -128, and the +above example contains two such values. So we make two tweaks: - (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 co_lnotab desiring to find the source line number - corresponding to a bytecode address A should do something like this + (a) there's a deep assumption that byte code offsets increase monotonically, + and + (b) if byte code offset jumps by more than 255 from one row to the next, or if + source code line number jumps by more than 127 or less than -128 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 co_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 co_lnotab: addr += addr_incr if addr > A: return lineno + if line_incr >= 0x80: + line_incr -= 0x100 lineno += line_incr (In C, this is implemented by PyCode_Addr2Line().) 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 in compile.c should not (as was actually done -until 2.2) expand 300, 300 to +until 2.2) expand 300, 200 to 255, 255, 45, 45, but to - 255, 0, 45, 255, 0, 45. + 255, 0, 45, 128, 0, 72. The above is sufficient to reconstruct line numbers for tracebacks, but not for line tracing. Tracing is handled by PyCode_CheckLineNumber() in codeobject.c |