Is there an easy way to remove comments from a C/C++ source file without doing any preprocessing. (ie, I think you can use gcc -E but this will expand macros.) I just want the source code with comments stripped, nothing else should be changed.
EDIT:
Preference towards an existing tool. I don't want to have to write this myself with regexes, I foresee too many surprises in the code.
Thanks to KennyTM for finding the right flags. Here’s the result for completeness:
test.c:
#define foo bar
foo foo foo
#ifdef foo
#undef foo
#define foo baz
#endif
foo foo
/* comments? comments. */
// c++ style comments
gcc -fpreprocessed -dD -E test.c:
#define foo bar
foo foo foo
#ifdef foo
#undef foo
#define foo baz
#endif
foo foo
See this answer here on SO for a similar question posted on a previous occasion...
Hope this helps, Best regards, Tom.
It depends on how perverse your comments are. I have a program scc to strip C and C++ comments. I also have a test file for it, and I tried GCC (4.2.1 on MacOS X) with the options in the currently selected answer - and GCC doesn't seem to do a perfect job on some of the horribly butchered comments in the test case.
Consider the (subset - 36 of 135 lines total) of the test case:
/\
*\
Regular
comment
*\
/
The regular C comment number 1 has finished.
/\
\/ This is not a C++/C99 comment!
This is followed by C++/C99 comment number 3.
/\
\
\
/ But this is a C++/C99 comment!
The C++/C99 comment number 3 has finished.
/\
\* This is not a C or C++ comment!
This is followed by regular C comment number 2.
/\
*/ This is a regular C comment *\
but this is just a routine continuation *\
and that was not the end either - but this is *\
\
/
The regular C comment number 2 has finished.
This is followed by regular C comment number 3.
/\
\
\
\
* C comment */
On my Mac, the output from GCC (gcc -fpreprocessed -dD -E subset.c) is:
/\
*\
Regular
comment
*\
/
The regular C comment number 1 has finished.
/\
\/ This is not a C++/C99 comment!
This is followed by C++/C99 comment number 3.
/\
\
\
/ But this is a C++/C99 comment!
The C++/C99 comment number 3 has finished.
/\
\* This is not a C or C++ comment!
This is followed by regular C comment number 2.
/\
*/ This is a regular C comment *\
but this is just a routine continuation *\
and that was not the end either - but this is *\
\
/
The regular C comment number 2 has finished.
This is followed by regular C comment number 3.
/\
\
\
\
* C comment */
The output from 'scc' is:
The regular C comment number 1 has finished.
/\
\/ This is not a C++/C99 comment!
This is followed by C++/C99 comment number 3.
/\
\
\
/ But this is a C++/C99 comment!
The C++/C99 comment number 3 has finished.
/\
\* This is not a C or C++ comment!
This is followed by regular C comment number 2.
The regular C comment number 2 has finished.
This is followed by regular C comment number 3.
The output from 'scc -C' (which recognizes double-slash comments) is:
The regular C comment number 1 has finished.
/\
\/ This is not a C++/C99 comment!
This is followed by C++/C99 comment number 3.
The C++/C99 comment number 3 has finished.
/\
\* This is not a C or C++ comment!
This is followed by regular C comment number 2.
The regular C comment number 2 has finished.
This is followed by regular C comment number 3.
The source for SCC is about 270 lines of code plus two supporting library files (one that I use in almost all my programs, and one that I use in filter programs). Contact me if you need it (see my profile).
gcc -fpreprocessed -dD -E did not work for me but this program does it:
#include <stdio.h>
static void process(FILE *f)
{
int c;
while ( (c=getc(f)) != EOF )
{
if (c=='\'' || c=='"') /* literal */
{
int q=c;
do
{
putchar(c);
if (c=='\\') putchar(getc(f));
c=getc(f);
} while (c!=q);
putchar(c);
}
else if (c=='/') /* opening comment ? */
{
c=getc(f);
if (c!='*') /* no, recover */
{
putchar('/');
ungetc(c,f);
}
else
{
int p;
putchar(' '); /* replace comment with space */
do
{
p=c;
c=getc(f);
} while (c!='/' || p!='*');
}
}
else
{
putchar(c);
}
}
}
int main(int argc, char *argv[])
{
process(stdin);
return 0;
}