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#line takes effect inside skipped groups and does not expand macros #734
Description
simplecpp handles #line while the file is read (TokenList::readfile), before conditional inclusion and macros are processed. A
#line in a skipped group therefore still changes the line numbers, and a #line whose operands are macros is ignored.
#if 0
#line 100
#endif
__LINE__gcc: 4. simplecpp: 101.
Inside a skipped group
| Input | gcc | simplecpp |
|---|---|---|
#if 0 / #line 100 / #endif / __LINE__ |
4 |
101 |
#ifdef X / #line 100 / #endif / __LINE__ |
4 |
101 |
#if 0 / #line 100 "x.c" / #endif / __FILE__ |
"c.c" |
"x.c" |
#if 0 / #line -5 / #endif / int x; |
int x; |
error: Invalid character in line directive: '-'. (all output is lost) |
Operands are macros
The standard says the tokens after #line are macro-expanded when they don't match one of the two forms directly (C11 §6.10.4p5, C++
[cpp.line]).
| Input | gcc | simplecpp |
|---|---|---|
#define L 200 / #line L / __LINE__ |
200 |
3 |
#define F "y.c" / #line 10 F / __FILE__ __LINE__ |
"y.c" 10 |
"c.c" 10 |
#define LF 20 "z.c" / #line LF / __FILE__ __LINE__ |
"z.c" 20 |
"c.c" 3 |
Already correct, and must stay correct: #line 10 "f.c" and the GCC line marker # 10 "m.c" (used in preprocessed .i files).
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