llvm/clang/test/Preprocessor/hash_line.c
Michael Kruse ae6b400002 [Preprocessor] Implement -fminimize-whitespace.
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
2021-07-25 23:30:57 -05:00

17 lines
406 B
C

// The 1 and # should not go on the same line.
// RUN: %clang_cc1 -E %s | FileCheck --strict-whitespace %s
// CHECK: {{^1$}}
// CHECK-NEXT: {{^ #$}}
// CHECK-NEXT: {{^2$}}
// CHECK-NEXT: {{^ #$}}
// RUN: %clang_cc1 -E -P -fminimize-whitespace %s | FileCheck --strict-whitespace %s --check-prefix=MINWS
// MINWS: {{^}}1#2#{{$}}
#define EMPTY
#define IDENTITY(X) X
1
EMPTY #
2
IDENTITY() #