The implementation of -fminimize-whitespace (D104601) revised the logic
when to emit newlines. There was no case to handle when more than
8 lines were skippped in -P (DisableLineMarkers) mode and instead fell
through the case intended for -fminimize-whitespace, i.e. emit nothing.
This patch will emit one newline in this case.
The newline logic is slightly reorganized. The `-P -fminimize-whitespace`
case is handled explicitly and emitting at least one newline is the new
fallback case. The choice between emitting a line marker or up to
7 empty lines is now a choice only with enabled line markers. The up to
8 newlines likely are fewer characters than a line directive, but
in -P mode this had the paradoxic effect that it would print up to
7 empty lines, but none at all if more than 8 lines had to be skipped.
Now with DisableLineMarkers, we don't consider printing empty lines
(just start a new line) which matches gcc's behavior.
The line-directive-output-mincol.c test is replaced with a more
comprehensive test skip-empty-lines.c also testing the more than
8 skipped lines behaviour with all flag combinations.
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D106924
This patch adds the -fminimize-whitespace with the following effects:
* If combined with -E, remove as much non-line-breaking whitespace as
possible.
* If combined with -E -P, removes as much whitespace as possible,
including line-breaks.
The motivation is to reduce the amount of insignificant changes in the
preprocessed output with source files where only whitespace has been
changed (add/remove comments, clang-format, etc.) which is in particular
useful with ccache.
A patch for ccache for using this flag has been proposed to ccache as well:
https://github.com/ccache/ccache/pull/815, which will use
-fnormalize-whitespace when clang-13 has been detected, and additionally
uses -P in "unify_mode". ccache already had a unify_mode in an older
version which was removed because of problems that using the
preprocessor itself does not have (such that the custom tokenizer did
not recognize C++11 raw strings).
This patch slightly reorganizes which part is responsible for adding
newlines that are required for semantics. It is now either
startNewLineIfNeeded() or MoveToLine() but never both; this avoids the
ShouldUpdateCurrentLine workaround and avoids redundant lines being
inserted in some cases. It also fixes a mandatory newline not inserted
after a _Pragma("...") that is expanded into a #pragma.
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D104601
Michael Kruse