python regex to match multi-line preprocessor macro
What follows is a regular expression I have written to match multi-line pre-processor macros in C / C++ code. I'm by no means a regular expressions guru, so I'd welcome any advice on how I can make this better.
Here's the regex:
\s*#define(.*\\\n)+[\S]+(?!\\)
It should match all of this:
#define foo(x) if(x) \
doSomething(x)
But only some of this (shouldn't match the next line of code:
#define foo(x) if(x) \
doSomething(x)
normalCode();
And also shouldn't match single-line preprocessor macros.
I'm pretty sure that the regex above works - but as I said, there probably a better way of doing it, and I imagine that there are ways of breaking it. Can anyone suggest any?
Asked by: Thomas187 | Posted: 28-01-2022
Answer 1
This is a simple test program I knocked up:
#!/usr/bin/env python
TEST1="""
#include "Foo.h"
#define bar foo\\
x
#include "Bar.h"
"""
TEST2="""
#define bar foo
#define x 1 \\
12 \\
2 \\\\ 3
Foobar
"""
TEST3="""
#define foo(x) if(x) \\
doSomething(x)
"""
TEST4="""
#define foo(x) if(x) \\
doSomething(x)
normalCode();
"""
import re
matcher = re.compile(r"^[ \t]*#define(.*\\\n)+.*$",re.MULTILINE)
def extractDefines(s):
mo = matcher.search(s)
if not mo:
print mo
return
print mo.group(0)
extractDefines(TEST1)
extractDefines(TEST2)
extractDefines(TEST3)
extractDefines(TEST4)
The re I used:
r"^[ \t]*#define(.*\\\n)+.*$"
Is very similar to the one use used, the changes:
- [ \t] To avoid newlines at the start of the define.
- I rely on + being greedy, so I can use a simple .*$ at the end to get the first line of the define that doesn't end with \
Answer 2
start = r"^\s*#define\s+"
continuation = r"(?:.*\\\n)+"
lastline = r".*$"
re_multiline_macros = re.compile(start + continuation + lastline,
re.MULTILINE)
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