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#174 remove line markers from output using -P on the command line #704

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#174 remove line markers from output using -P on the command line #704

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7 changes: 7 additions & 0 deletions main.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -153,6 +153,12 @@ int main(int argc, char **argv)
found = true;
}
break;
case 'P':
if (std::strcmp(arg, "-P")==0) {
dui.ignoreLineDirectives = true;
found = true;
}
break;
}
if (!found) {
std::cout << "error: option '" << arg << "' is unknown." << std::endl;
Expand Down Expand Up @@ -187,6 +193,7 @@ int main(int argc, char **argv)
std::cout << " -e Output errors only." << std::endl;
std::cout << " -f Fail when errors were encountered (exitcode 1)." << std::endl;
std::cout << " -l Print lines numbers." << std::endl;
std::cout << " -P Ignore #line / # <num> \"file\" directives (do not let them affect location tracking)." << std::endl;
return 0;
}

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5 changes: 3 additions & 2 deletions simplecpp.cpp
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Expand Up @@ -799,7 +799,8 @@ void simplecpp::TokenList::readfile(Stream &stream, const std::string &filename,
else
fileindex = location.fileIndex;

lineDirective(fileindex, line, location);
if (!dui.ignoreLineDirectives)

@danmar danmar Oct 1, 2026

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This is an AI review take it with a grain of salt. Please feel free to reject it by clicking on Resolve

I don't think this implements what #174 asks for. gcc -E -P suppresses the linemarkers in the output; it does not ignore #line directives in the input. In simplecpp the output markers come from TokenList::stringify(), which writes #line N "file" whenever the file changes or the line goes backwards. Those are untouched by this PR, so includes still produce markers:

$ cat a.h
int h;
$ cat m.c
#include "a.h"
int x;
#line 10 "foo.c"
int y;
$ ./simplecpp -P m.c

#line 1 "a.h"
int h ;
#line 2 "m.c"
int x ;

int y ;

Ignoring input #line also changes semantics in a way gcc's -P does not: __LINE__/__FILE__ and the locations in error messages no longer follow the #line directive (with gcc -E -P, #line 10 "foo.c" still affects __LINE__/__FILE__).

Suggestion: make this an output option instead, e.g. a parameter to stringify() (or a separate print loop in main.cpp) that skips writing the #line markers, and leave the tokenizer/DUI unchanged.

lineDirective(fileindex, line, location);
}

continue;
Expand Down Expand Up @@ -3223,7 +3224,7 @@ std::pair<simplecpp::FileData *, bool> simplecpp::FileDataCache::tryload(FileDat
return {id_it->second, false};
}

auto *const data = new FileData {path, TokenList(path, filenames, {}, outputList)};
auto *const data = new FileData {path, TokenList(path, filenames, dui, outputList)};

@danmar danmar Oct 1, 2026

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This is an AI review take it with a grain of salt. Please feel free to reject it by clicking on Resolve

Passing dui here instead of {} changes behaviour for all library users, not just -P: readfile() uses dui.std for the #line portability diagnostics, so headers will now get std-specific messages they didn't get before. That may be a good change, but it is unrelated to -P. If the option becomes output-only (see the other comment), this change isn't needed. If it is kept, it would be good to mention it in the PR description and add a test for it.


if (dui.removeComments)
data->tokens.removeComments();
Expand Down
3 changes: 2 additions & 1 deletion simplecpp.h
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Expand Up @@ -265,7 +265,7 @@ namespace simplecpp {

/**
* Command line preprocessor settings.
* On the command line these are configured by -D, -U, -I, --include, -std
* On the command line these are configured by -D, -U, -I, --include, -std, -P
*/
struct SIMPLECPP_LIB DUI {
DUI() = default;
Expand All @@ -276,6 +276,7 @@ namespace simplecpp {
std::string std;
bool clearIncludeCache{};
bool removeComments{}; /** remove comment tokens from included files */
bool ignoreLineDirectives{}; /** -P: do not let #line directives affect location tracking */
};

/** List of tokens. */
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14 changes: 14 additions & 0 deletions test.cpp
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Expand Up @@ -2731,6 +2731,19 @@ static void location12()
}


static void location13()

@danmar danmar Oct 1, 2026

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This is an AI review take it with a grain of salt. Please feel free to reject it by clicking on Resolve

This test only covers a #line directive in the main file. The more common case for -P (e.g. creduce input) is output that crosses #include boundaries, and that currently still prints #line markers. A test that uses an include, and checks that the stringified output has no #line lines, would catch that.

{
simplecpp::DUI dui;
dui.ignoreLineDirectives = true;

const char code[] =
"#line 3 \"file.c\"\n"
"__LINE__ __FILE__\n";
ASSERT_EQUALS("\n"
"2 \"\"",
preprocess(code, dui));
}

static void missingHeader1()
{
const char code[] = "#include \"notexist.h\"\n";
Expand Down Expand Up @@ -4750,6 +4763,7 @@ static void runTests(int argc, char **argv, Input input)
TEST_CASE(location10);
TEST_CASE(location11);
TEST_CASE(location12);
TEST_CASE(location13);

TEST_CASE(missingHeader1);
TEST_CASE(missingHeader2);
Expand Down
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