[clang-tools-extra] r361225 - [clang-tidy] New option for misc-throw-by-value-catch-by-reference
Adam Balogh via cfe-commits
cfe-commits at lists.llvm.org
Tue May 21 00:25:06 PDT 2019
Author: baloghadamsoftware
Date: Tue May 21 00:25:06 2019
New Revision: 361225
URL: http://llvm.org/viewvc/llvm-project?rev=361225&view=rev
Log:
[clang-tidy] New option for misc-throw-by-value-catch-by-reference
Catching trivial objects by value is not dangerous but may be
inefficient if they are too large. This patch adds an option
`WarnOnLargeObject` to the checker to also warn if such an object
is caught by value. An object is considered as "large" if its
size is greater than `MaxSize` which is another option. Default
value is the machine word of the architecture (size of the type
`size_t`).
Differential Revision: https://reviews.llvm.org/D61851
Modified:
clang-tools-extra/trunk/clang-tidy/misc/ThrowByValueCatchByReferenceCheck.cpp
clang-tools-extra/trunk/clang-tidy/misc/ThrowByValueCatchByReferenceCheck.h
clang-tools-extra/trunk/docs/ReleaseNotes.rst
clang-tools-extra/trunk/docs/clang-tidy/checks/misc-throw-by-value-catch-by-reference.rst
Modified: clang-tools-extra/trunk/clang-tidy/misc/ThrowByValueCatchByReferenceCheck.cpp
URL: http://llvm.org/viewvc/llvm-project/clang-tools-extra/trunk/clang-tidy/misc/ThrowByValueCatchByReferenceCheck.cpp?rev=361225&r1=361224&r2=361225&view=diff
==============================================================================
--- clang-tools-extra/trunk/clang-tidy/misc/ThrowByValueCatchByReferenceCheck.cpp (original)
+++ clang-tools-extra/trunk/clang-tidy/misc/ThrowByValueCatchByReferenceCheck.cpp Tue May 21 00:25:06 2019
@@ -20,7 +20,10 @@ namespace misc {
ThrowByValueCatchByReferenceCheck::ThrowByValueCatchByReferenceCheck(
StringRef Name, ClangTidyContext *Context)
: ClangTidyCheck(Name, Context),
- CheckAnonymousTemporaries(Options.get("CheckThrowTemporaries", true)) {}
+ CheckAnonymousTemporaries(Options.get("CheckThrowTemporaries", true)),
+ WarnOnLargeObject(Options.get("WarnOnLargeObject", false)),
+ // Cannot access `ASTContext` from here so set it to an extremal value.
+ MaxSize(Options.get("MaxSize", std::numeric_limits<uint64_t>::max())) {}
void ThrowByValueCatchByReferenceCheck::registerMatchers(MatchFinder *Finder) {
// This is a C++ only check thus we register the matchers only for C++
@@ -150,8 +153,19 @@ void ThrowByValueCatchByReferenceCheck::
// If it's not a pointer and not a reference then it must be caught "by
// value". In this case we should emit a diagnosis message unless the type
// is trivial.
- if (!caughtType.isTrivialType(context))
+ if (!caughtType.isTrivialType(context)) {
diag(varDecl->getBeginLoc(), diagMsgCatchReference);
+ } else if (WarnOnLargeObject) {
+ // If the type is trivial, then catching it by reference is not dangerous.
+ // However, catching large objects by value decreases the performance.
+
+ // We can now access `ASTContext` so if `MaxSize` is an extremal value
+ // then set it to the size of `size_t`.
+ if (MaxSize == std::numeric_limits<uint64_t>::max())
+ MaxSize = context.getTypeSize(context.getSizeType());
+ if (context.getTypeSize(caughtType) > MaxSize)
+ diag(varDecl->getBeginLoc(), diagMsgCatchReference);
+ }
}
}
Modified: clang-tools-extra/trunk/clang-tidy/misc/ThrowByValueCatchByReferenceCheck.h
URL: http://llvm.org/viewvc/llvm-project/clang-tools-extra/trunk/clang-tidy/misc/ThrowByValueCatchByReferenceCheck.h?rev=361225&r1=361224&r2=361225&view=diff
==============================================================================
--- clang-tools-extra/trunk/clang-tidy/misc/ThrowByValueCatchByReferenceCheck.h (original)
+++ clang-tools-extra/trunk/clang-tidy/misc/ThrowByValueCatchByReferenceCheck.h Tue May 21 00:25:06 2019
@@ -41,6 +41,8 @@ private:
bool isCatchVariable(const DeclRefExpr *declRefExpr);
bool isFunctionOrCatchVar(const DeclRefExpr *declRefExpr);
const bool CheckAnonymousTemporaries;
+ const bool WarnOnLargeObject;
+ uint64_t MaxSize; // No `const` because we have to set it in two steps.
};
} // namespace misc
Modified: clang-tools-extra/trunk/docs/ReleaseNotes.rst
URL: http://llvm.org/viewvc/llvm-project/clang-tools-extra/trunk/docs/ReleaseNotes.rst?rev=361225&r1=361224&r2=361225&view=diff
==============================================================================
--- clang-tools-extra/trunk/docs/ReleaseNotes.rst (original)
+++ clang-tools-extra/trunk/docs/ReleaseNotes.rst Tue May 21 00:25:06 2019
@@ -170,6 +170,11 @@ Improvements to clang-tidy
Rewrites function signatures to use a trailing return type.
+- The :doc:`misc-throw-by-value-catch-by-reference
+ <clang-tidy/misc-throw-by-value-catch-by-reference.rst>` now supports
+ `WarnOnLargeObject` and `MaxSize` options to warn on any large trivial
+ object caught by value.
+
Improvements to include-fixer
-----------------------------
Modified: clang-tools-extra/trunk/docs/clang-tidy/checks/misc-throw-by-value-catch-by-reference.rst
URL: http://llvm.org/viewvc/llvm-project/clang-tools-extra/trunk/docs/clang-tidy/checks/misc-throw-by-value-catch-by-reference.rst?rev=361225&r1=361224&r2=361225&view=diff
==============================================================================
--- clang-tools-extra/trunk/docs/clang-tidy/checks/misc-throw-by-value-catch-by-reference.rst (original)
+++ clang-tools-extra/trunk/docs/clang-tidy/checks/misc-throw-by-value-catch-by-reference.rst Tue May 21 00:25:06 2019
@@ -32,3 +32,18 @@ Options
<https://www.securecoding.cert.org/confluence/display/cplusplus/ERR09-CPP.+Throw+anonymous+temporaries>`_.
Default is `1`.
+.. option:: WarnOnLargeObject
+
+ Also warns for any large, trivial object caught by value. Catching a large
+ object by value is not dangerous but affects the performance negatively. The
+ maximum size of an object allowed to be caught without warning can be set
+ using the `MaxSize` option.
+ Default is `0`.
+
+.. option:: MaxSize
+
+ Determines the maximum size of an object allowed to be caught without
+ warning. Only applicable if `WarnOnLargeObject` is set to `1`. If option is
+ set by the user to `std::numeric_limits<uint64_t>::max()` then it reverts to
+ the default value.
+ Default is the size of `size_t`.
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