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annotate_ifdef_directives: remove some cases of double negation

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This change should reduce the number of cases where we say
"/* !(!defined(foo)) */" .

This only does cases where we can use a regex to make sure that the
simplification is guaranteed to be correct.  Full boolean
simplification would require this script to parse C, and nobody
wants that.
This commit is contained in:
Nick Mathewson 2019-09-18 10:59:35 -04:00
parent 16890839d3
commit 65e63e7461
1 changed files with 42 additions and 2 deletions
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44
scripts/maint/annotate_ifdef_directives
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@ -54,6 +54,46 @@ def commented_line(fmt, argument, maxwidth=LINE_WIDTH):
assert len(result) <= maxwidth
return result
def negate(expr):
"""Return a negated version of expr; try to avoid double-negation.
We usually wrap expressions in parentheses and add a "!".
>>> negate("A && B")
'!(A && B)'
But if we recognize the expression as negated, we can restore it.
>>> negate(negate("A && B"))
'A && B'
The same applies for defined(FOO).
>>> negate("defined(FOO)")
'!defined(FOO)'
>>> negate(negate("defined(FOO)"))
'defined(FOO)'
Internal parentheses don't confuse us:
>>> negate("!(FOO) && !(BAR)")
'!(!(FOO) && !(BAR))'
"""
expr = expr.strip()
# See whether we match !(...), with no intervening close-parens.
m = re.match(r'^!\s*\(([^\)]*)\)$', expr)
if m:
return m.group(1)
# See whether we match !?defined(...), with no intervening close-parens.
m = re.match(r'^(!?)\s*(defined\([^\)]*\))$', expr)
if m:
if m.group(1) == "!":
prefix = ""
else:
prefix = "!"
return prefix + m.group(2)
return "!(%s)" % expr
def uncomment(s):
"""
Remove existing trailing comments from an #else or #endif line.
@ -108,8 +148,8 @@ def translate(f_in, f_out):
raise Problem("Unexpected #%s on %d"% (command,lineno))
if (len(cur_level) == 1 and command == 'else' and
lineno > cur_level[0][2] + LINE_OBVIOUSNESS_LIMIT):
f_out.write(commented_line("#else /* !(%s) */\n",
cur_level[0][1]))
f_out.write(commented_line("#else /* %s */\n",
negate(cur_level[0][1])))
else:
f_out.write(line)
cur_level.append((command, rest, lineno))