From: Alexander Kornienko <alexfh@google.com>
Date: Wed, 19 Jun 2013 19:50:11 +0000 (+0000)
Subject: Fixed long-standing issue with incorrect length calculation of multi-line comments.
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=c36c5c247f53b0517b141ae5ae93f4580e9452ba;p=clang

Fixed long-standing issue with incorrect length calculation of multi-line comments.

Summary:
A trailing block comment having multiple lines would cause extremely
high penalties if the summary length of its lines is more than the column limit.
Fixed by always considering only the last line of a multi-line block comment.
Removed a long-standing FIXME from relevant tests and added a motivating test
modelled after problem cases from real code.

Reviewers: klimek

Reviewed By: klimek

CC: cfe-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D1010

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@184340 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Format/Format.cpp b/lib/Format/Format.cpp
index 14337e9760..86437d4c18 100644
--- a/lib/Format/Format.cpp
+++ b/lib/Format/Format.cpp
@@ -832,17 +832,17 @@ private:
     }
     if (Current.UnbreakableTailLength >= getColumnLimit())
       return 0;
-    unsigned RemainingSpace = getColumnLimit() - Current.UnbreakableTailLength;
 
+    unsigned RemainingSpace = getColumnLimit() - Current.UnbreakableTailLength;
     bool BreakInserted = false;
     unsigned Penalty = 0;
-    unsigned PositionAfterLastLineInToken = 0;
+    unsigned RemainingTokenColumns = 0;
     for (unsigned LineIndex = 0, EndIndex = Token->getLineCount();
          LineIndex != EndIndex; ++LineIndex) {
       if (!DryRun)
         Token->replaceWhitespaceBefore(LineIndex, Whitespaces);
       unsigned TailOffset = 0;
-      unsigned RemainingTokenColumns = Token->getLineLengthAfterSplit(
+      RemainingTokenColumns = Token->getLineLengthAfterSplit(
           LineIndex, TailOffset, StringRef::npos);
       while (RemainingTokenColumns > RemainingSpace) {
         BreakableToken::Split Split =
@@ -868,11 +868,11 @@ private:
         RemainingTokenColumns = NewRemainingTokenColumns;
         BreakInserted = true;
       }
-      PositionAfterLastLineInToken = RemainingTokenColumns;
     }
 
+    State.Column = RemainingTokenColumns;
+
     if (BreakInserted) {
-      State.Column = PositionAfterLastLineInToken;
       // If we break the token inside a parameter list, we need to break before
       // the next parameter on all levels, so that the next parameter is clearly
       // visible. Line comments already introduce a break.
diff --git a/unittests/Format/FormatTest.cpp b/unittests/Format/FormatTest.cpp
index 15a5d6b574..f20eca1119 100644
--- a/unittests/Format/FormatTest.cpp
+++ b/unittests/Format/FormatTest.cpp
@@ -755,7 +755,7 @@ TEST_F(FormatTest, RemovesTrailingWhitespaceOfComments) {
                    getLLVMStyleWithColumns(33)));
 }
 
-TEST_F(FormatTest, UnderstandsMultiLineComments) {
+TEST_F(FormatTest, UnderstandsBlockComments) {
   verifyFormat("f(/*test=*/ true);");
   EXPECT_EQ(
       "f(aaaaaaaaaaaaaaaaaaaaaaaaa, /* Trailing comment for aa... */\n"
@@ -786,7 +786,7 @@ TEST_F(FormatTest, UnderstandsMultiLineComments) {
                NoBinPacking);
 }
 
-TEST_F(FormatTest, AlignsMultiLineComments) {
+TEST_F(FormatTest, AlignsBlockComments) {
   EXPECT_EQ("/*\n"
             " * Really multi-line\n"
             " * comment.\n"
@@ -836,6 +836,13 @@ TEST_F(FormatTest, AlignsMultiLineComments) {
                    "        * line. */"));
 }
 
+TEST_F(FormatTest, CorrectlyHandlesLengthOfBlockComments) {
+  EXPECT_EQ("double *x; /* aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\n"
+            "              aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa */",
+            format("double *x; /* aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\n"
+                   "              aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa */"));
+}
+
 TEST_F(FormatTest, SplitsLongCxxComments) {
   EXPECT_EQ("// A comment that\n"
             "// doesn't fit on\n"
@@ -919,24 +926,19 @@ TEST_F(FormatTest, PriorityOfCommentBreaking) {
 }
 
 TEST_F(FormatTest, MultiLineCommentsInDefines) {
-  // FIXME: The line breaks are still suboptimal (current guess
-  // is that this is due to the token length being misused), but
-  // the comment handling is correct.
-  EXPECT_EQ("#define A(      \\\n"
-            "    x) /*       \\\n"
-            "a comment       \\\n"
-            "inside */       \\\n"
+  EXPECT_EQ("#define A(x) /* \\\n"
+            "  a comment     \\\n"
+            "  inside */     \\\n"
             "  f();",
             format("#define A(x) /* \\\n"
                    "  a comment     \\\n"
                    "  inside */     \\\n"
                    "  f();",
                    getLLVMStyleWithColumns(17)));
-  EXPECT_EQ("#define A(x) /* \\\n"
-            "        a       \\\n"
-            "        comment \\\n"
-            "        inside  \\\n"
-            "        */      \\\n"
+  EXPECT_EQ("#define A(      \\\n"
+            "    x) /*       \\\n"
+            "  a comment     \\\n"
+            "  inside */     \\\n"
             "  f();",
             format("#define A(      \\\n"
                    "    x) /*       \\\n"