<div dir="ltr"><div class="gmail_extra"><div class="gmail_quote">Thanks for writing the check! It would be better though, if you sent the code for pre-commit review, especially as you are adding a new check.</div><div class="gmail_quote">
<br></div><div class="gmail_quote">Did you run the check over the whole LLVM/Clang source code? Could you share the results? (Number of warnings and false-positive rate in a sample of a few tens of instances.)</div><div class="gmail_quote">
<br></div><div class="gmail_quote">On Tue, Jul 8, 2014 at 3:32 PM, Benjamin Kramer <span dir="ltr"><<a href="mailto:benny.kra@googlemail.com" target="_blank">benny.kra@googlemail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
Author: d0k<br>
Date: Tue Jul 8 09:32:17 2014<br>
New Revision: 212535<br>
<br>
URL: <a href="http://llvm.org/viewvc/llvm-project?rev=212535&view=rev" target="_blank">http://llvm.org/viewvc/llvm-project?rev=212535&view=rev</a><br>
Log:<br>
[clang-tidy] Add a little checker for Twine locals in LLVM.<br>
<br>
Those often cause use after free bugs and should be generally avoided.<br>
Technically it is safe to have a Twine with >=2 components in a variable<br>
but I don't think it is a good pattern to follow. The almost trivial checker<br>
comes with elaborated fix-it hints that turn the Twine into a std::string<br>
if necessary and otherwise fall back to the original type if the Twine<br>
is created from a single value.<br>
<br>
Added:<br>
clang-tools-extra/trunk/clang-tidy/llvm/TwineLocalCheck.cpp<br>
clang-tools-extra/trunk/clang-tidy/llvm/TwineLocalCheck.h<br>
clang-tools-extra/trunk/test/clang-tidy/llvm-twine-local.cpp<br>
Modified:<br>
clang-tools-extra/trunk/clang-tidy/llvm/CMakeLists.txt<br>
clang-tools-extra/trunk/clang-tidy/llvm/LLVMTidyModule.cpp<br>
<br>
Modified: clang-tools-extra/trunk/clang-tidy/llvm/CMakeLists.txt<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/clang-tools-extra/trunk/clang-tidy/llvm/CMakeLists.txt?rev=212535&r1=212534&r2=212535&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/clang-tools-extra/trunk/clang-tidy/llvm/CMakeLists.txt?rev=212535&r1=212534&r2=212535&view=diff</a><br>
==============================================================================<br>
--- clang-tools-extra/trunk/clang-tidy/llvm/CMakeLists.txt (original)<br>
+++ clang-tools-extra/trunk/clang-tidy/llvm/CMakeLists.txt Tue Jul 8 09:32:17 2014<br>
@@ -4,6 +4,7 @@ add_clang_library(clangTidyLLVMModule<br>
IncludeOrderCheck.cpp<br>
LLVMTidyModule.cpp<br>
NamespaceCommentCheck.cpp<br>
+ TwineLocalCheck.cpp<br>
<br>
LINK_LIBS<br>
clangAST<br>
<br>
Modified: clang-tools-extra/trunk/clang-tidy/llvm/LLVMTidyModule.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/clang-tools-extra/trunk/clang-tidy/llvm/LLVMTidyModule.cpp?rev=212535&r1=212534&r2=212535&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/clang-tools-extra/trunk/clang-tidy/llvm/LLVMTidyModule.cpp?rev=212535&r1=212534&r2=212535&view=diff</a><br>
==============================================================================<br>
--- clang-tools-extra/trunk/clang-tidy/llvm/LLVMTidyModule.cpp (original)<br>
+++ clang-tools-extra/trunk/clang-tidy/llvm/LLVMTidyModule.cpp Tue Jul 8 09:32:17 2014<br>
@@ -12,6 +12,7 @@<br>
#include "../ClangTidyModuleRegistry.h"<br>
#include "IncludeOrderCheck.h"<br>
#include "NamespaceCommentCheck.h"<br>
+#include "TwineLocalCheck.h"<br>
<br>
namespace clang {<br>
namespace tidy {<br>
@@ -24,6 +25,9 @@ public:<br>
CheckFactories.addCheckFactory(<br>
"llvm-namespace-comment",<br>
new ClangTidyCheckFactory<NamespaceCommentCheck>());<br>
+ CheckFactories.addCheckFactory(<br>
+ "llvm-twine-local",<br>
+ new ClangTidyCheckFactory<TwineLocalCheck>());<br>
}<br>
};<br>
<br>
<br>
Added: clang-tools-extra/trunk/clang-tidy/llvm/TwineLocalCheck.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/clang-tools-extra/trunk/clang-tidy/llvm/TwineLocalCheck.cpp?rev=212535&view=auto" target="_blank">http://llvm.org/viewvc/llvm-project/clang-tools-extra/trunk/clang-tidy/llvm/TwineLocalCheck.cpp?rev=212535&view=auto</a><br>
==============================================================================<br>
--- clang-tools-extra/trunk/clang-tidy/llvm/TwineLocalCheck.cpp (added)<br>
+++ clang-tools-extra/trunk/clang-tidy/llvm/TwineLocalCheck.cpp Tue Jul 8 09:32:17 2014<br>
@@ -0,0 +1,64 @@<br>
+//===--- TwineLocalCheck.cpp - clang-tidy ---------------------------------===//<br>
+//<br>
+// The LLVM Compiler Infrastructure<br>
+//<br>
+// This file is distributed under the University of Illinois Open Source<br>
+// License. See LICENSE.TXT for details.<br>
+//<br>
+//===----------------------------------------------------------------------===//<br>
+<br>
+#include "TwineLocalCheck.h"<br>
+#include "clang/AST/ASTContext.h"<br>
+#include "clang/ASTMatchers/ASTMatchers.h"<br>
+#include "clang/Lex/Lexer.h"<br>
+#include "llvm/Support/raw_ostream.h"<br></blockquote><div><br></div><div>Is this header needed?</div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
+<br>
+using namespace clang::ast_matchers;<br>
+<br>
+namespace clang {<br>
+namespace tidy {<br>
+<br>
+TwineLocalCheck::TwineLocalCheck() {}<br>
+<br>
+void TwineLocalCheck::registerMatchers(MatchFinder *Finder) {<br>
+ auto TwineType =<br>
+ qualType(hasDeclaration(recordDecl(hasName("::llvm::Twine"))));<br>
+ Finder->addMatcher(varDecl(hasType(TwineType)).bind("variable"), this);<br>
+}<br>
+<br>
+void TwineLocalCheck::check(const MatchFinder::MatchResult &Result) {<br>
+ const VarDecl *VD = Result.Nodes.getNodeAs<VarDecl>("variable");<br>
+ auto Diag = diag(VD->getLocation(),<br>
+ "twine variables are prone to use after free bugs");<br></blockquote><div><br></div><div>I'm not a native speaker, but "use-after-free" looks more correct to me.</div><div> </div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
+<br>
+ // If this VarDecl has an initializer try to fix it.<br>
+ if (VD->hasInit()) {<br>
+ // Peel away implicit constructors and casts so we can see the actual type<br>
+ // of the initializer.<br>
+ const Expr *C = VD->getInit();<br>
+ while (isa<CXXConstructExpr>(C))<br>
+ C = cast<CXXConstructExpr>(C)->getArg(0)->IgnoreParenImpCasts();<br></blockquote><div><br></div><div>Maybe</div><div> while (auto Ctor = dyn_cast<CXXConstructExpr>(C))</div><div> C = Ctor->getArg(0)->IgnoreParenImpCasts();</div>
<div>?</div><div><br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
+<br>
+ SourceRange TypeRange =<br>
+ VD->getTypeSourceInfo()->getTypeLoc().getSourceRange();<br>
+<br>
+ // A real Twine, turn it into a std::string.<br>
+ if (VD->getType()->getCanonicalTypeUnqualified() ==<br>
+ C->getType()->getCanonicalTypeUnqualified()) {<br>
+ SourceLocation EndLoc = Lexer::getLocForEndOfToken(<br>
+ VD->getInit()->getLocEnd(), 0, *Result.SourceManager,<br>
+ Result.Context->getLangOpts());<br>
+ Diag << FixItHint::CreateReplacement(TypeRange, "std::string")<br>
+ << FixItHint::CreateInsertion(VD->getInit()->getLocStart(), "(")<br>
+ << FixItHint::CreateInsertion(EndLoc, ").str()");<br>
+ } else {<br>
+ // Just an implicit conversion. Insert the real type.<br>
+ Diag << FixItHint::CreateReplacement(<br>
+ TypeRange,<br>
+ C->getType().getAsString(Result.Context->getPrintingPolicy()));<br>
+ }<br>
+ }<br>
+}<br>
+<br>
+} // namespace tidy<br>
+} // namespace clang<br>
<br>
Added: clang-tools-extra/trunk/clang-tidy/llvm/TwineLocalCheck.h<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/clang-tools-extra/trunk/clang-tidy/llvm/TwineLocalCheck.h?rev=212535&view=auto" target="_blank">http://llvm.org/viewvc/llvm-project/clang-tools-extra/trunk/clang-tidy/llvm/TwineLocalCheck.h?rev=212535&view=auto</a><br>
==============================================================================<br>
--- clang-tools-extra/trunk/clang-tidy/llvm/TwineLocalCheck.h (added)<br>
+++ clang-tools-extra/trunk/clang-tidy/llvm/TwineLocalCheck.h Tue Jul 8 09:32:17 2014<br>
@@ -0,0 +1,31 @@<br>
+//===--- TwineLocalCheck.h - clang-tidy -------------------------*- C++ -*-===//<br>
+//<br>
+// The LLVM Compiler Infrastructure<br>
+//<br>
+// This file is distributed under the University of Illinois Open Source<br>
+// License. See LICENSE.TXT for details.<br>
+//<br>
+//===----------------------------------------------------------------------===//<br>
+<br>
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_LLVM_TWINE_LOCAL_CHECK_H<br>
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_LLVM_TWINE_LOCAL_CHECK_H<br>
+<br>
+#include "../ClangTidy.h"<br>
+#include "llvm/Support/Regex.h"<br></blockquote><div><br></div><div>Do you need this include?</div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
+<br>
+namespace clang {<br>
+namespace tidy {<br>
+<br>
+/// \brief Looks for local Twine variables which are prone to use after frees<br>
+/// and should be generally avoided.<br>
+class TwineLocalCheck : public ClangTidyCheck {<br>
+public:<br>
+ TwineLocalCheck();<br>
+ void registerMatchers(ast_matchers::MatchFinder *Finder) override;<br>
+ void check(const ast_matchers::MatchFinder::MatchResult &Result) override;<br>
+};<br>
+<br>
+} // namespace tidy<br>
+} // namespace clang<br>
+<br>
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_LLVM_TWINE_LOCAL_CHECK_H<br>
<br>
Added: clang-tools-extra/trunk/test/clang-tidy/llvm-twine-local.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/clang-tools-extra/trunk/test/clang-tidy/llvm-twine-local.cpp?rev=212535&view=auto" target="_blank">http://llvm.org/viewvc/llvm-project/clang-tools-extra/trunk/test/clang-tidy/llvm-twine-local.cpp?rev=212535&view=auto</a><br>
==============================================================================<br>
--- clang-tools-extra/trunk/test/clang-tidy/llvm-twine-local.cpp (added)<br>
+++ clang-tools-extra/trunk/test/clang-tidy/llvm-twine-local.cpp Tue Jul 8 09:32:17 2014<br>
@@ -0,0 +1,35 @@<br>
+// RUN: grep -Ev "// *[A-Z-]+:" %s > %t.cpp<br>
+// RUN: clang-tidy %t.cpp -checks='-*,llvm-twine-local' -fix -- > %t.msg 2>&1<br>
+// RUN: FileCheck -input-file=%t.cpp %s </blockquote><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
+// RUN: FileCheck -input-file=%t.msg -check-prefix=CHECK-MESSAGES %s<br></blockquote><div><br></div><div>It's a nice idea to test both messages and fixes simultaneously. Maybe you can update check_clang_tidy_fix.sh and tests that use it?</div>
<div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
+<br>
+namespace llvm {<br>
+class Twine {<br>
+public:<br>
+ Twine(const char *);<br>
+ Twine(int);<br>
+ Twine &operator+(const Twine &);<br>
+};<br>
+}<br>
+<br>
+using namespace llvm;<br>
+<br>
+void foo(const Twine &x);<br>
+<br>
+static Twine Moo = Twine("bark") + "bah";<br>
+// CHECK-MASSAGES: twine variables are prone to use after free bugs<br>
+// CHECK-MESSAGES: note: FIX-IT applied suggested code changes<br>
+// CHECK: static std::string Moo = (Twine("bark") + "bah").str();<br>
+<br>
+int main() {<br>
+ const Twine t = Twine("a") + "b" + Twine(42);<br>
+// CHECK-MASSAGES: twine variables are prone to use after free bugs<br>
+// CHECK-MESSAGES: note: FIX-IT applied suggested code changes<br>
+// CHECK: std::string t = (Twine("a") + "b" + Twine(42)).str();<br>
+ foo(Twine("a") + "b");<br>
+<br>
+ Twine Prefix = false ? "__INT_FAST" : "__UINT_FAST";<br>
+// CHECK-MASSAGES: twine variables are prone to use after free bugs<br>
+// CHECK-MESSAGES: note: FIX-IT applied suggested code changes<br>
+// CHECK: const char * Prefix = false ? "__INT_FAST" : "__UINT_FAST";<br>
+}<br>
<br>
<br>
_______________________________________________<br>
cfe-commits mailing list<br>
<a href="mailto:cfe-commits@cs.uiuc.edu" target="_blank">cfe-commits@cs.uiuc.edu</a><br>
<a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits" target="_blank">http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits</a><br>
</blockquote></div><br>
</div></div>