george.burgess.iv created this revision.
george.burgess.iv added reviewers: aaron.ballman, alexfh.
Herald added a subscriber: mgorny.
`TEMP_FAILURE_RETRY(x)` is a macro that executes `x` until `(x) != -1 || errno
!= EINTR`, and evaluates to the result of the last execution of `x`.
I've been told that a somewhat common mistake people make with this is to
include a condition in `TEMP_FAILURE_RETRY`'s argument, e.g.
// Wrote
TEMP_FAILURE_RETRY(foo() == 1)
// Meant
TEMP_FAILURE_RETRY(foo()) == 1
...In the former case, the `TEMP_FAILURE_RETRY` is useless, since `(x == 1) !=
-1` is always true. It will appear to work, though, since `TEMP_FAILURE_RETRY`
will execute `foo()` at least once, and it'll evaluate to the value of the
condition.
We do have a warning in clang to catch things like `(x == y) == -1`
(-Wtautological-constant-out-of-range-compare), and it does complain about this
in C++. However, we don't see these warnings in C, since `TEMP_FAILURE_RETRY`
stores the result of executing `x` into a temporary of type `typeof(x)`, and
comparisons are `int`s in C.
Repository:
rCTE Clang Tools Extra
https://reviews.llvm.org/D45059
Files:
clang-tidy/bugprone/BugproneTidyModule.cpp
clang-tidy/bugprone/CMakeLists.txt
clang-tidy/bugprone/ComparisonInTempFailureRetryCheck.cpp
clang-tidy/bugprone/ComparisonInTempFailureRetryCheck.h
docs/ReleaseNotes.rst
docs/clang-tidy/checks/bugprone-comparison-in-temp-failure-retry.rst
docs/clang-tidy/checks/list.rst
test/clang-tidy/bugprone-comparison-in-temp-failure-retry.c
Index: test/clang-tidy/bugprone-comparison-in-temp-failure-retry.c
===================================================================
--- /dev/null
+++ test/clang-tidy/bugprone-comparison-in-temp-failure-retry.c
@@ -0,0 +1,109 @@
+// RUN: %check_clang_tidy %s bugprone-comparison-in-temp-failure-retry %t
+
+#define TEMP_FAILURE_RETRY(x) \
+ ({ \
+ typeof(x) __z; \
+ do \
+ __z = (x); \
+ while (__z == -1); \
+ __z; \
+ })
+
+int foo();
+int bar(int a);
+
+void test() {
+ int i;
+ TEMP_FAILURE_RETRY((i = foo()));
+ TEMP_FAILURE_RETRY(foo());
+ TEMP_FAILURE_RETRY((foo()));
+
+ TEMP_FAILURE_RETRY(foo() == 1);
+ // CHECK-MESSAGES: :[[@LINE-1]]:28: warning: Top-level comparisons should be moved out of TEMP_FAILURE_RETRY [bugprone-comparison-in-temp-failure-retry]
+ TEMP_FAILURE_RETRY((foo() == 1));
+ // CHECK-MESSAGES: :[[@LINE-1]]:29: warning: Top-level comparisons should be moved out of TEMP_FAILURE_RETRY
+ TEMP_FAILURE_RETRY((int)(foo() == 1));
+ // CHECK-MESSAGES: :[[@LINE-1]]:34: warning: Top-level comparisons should be moved out of TEMP_FAILURE_RETRY
+
+ TEMP_FAILURE_RETRY(bar(foo() == 1));
+ TEMP_FAILURE_RETRY((bar(foo() == 1)));
+ TEMP_FAILURE_RETRY((bar(foo() == 1)) == 1);
+ // CHECK-MESSAGES: :[[@LINE-1]]:40: warning: Top-level comparisons should be moved out of TEMP_FAILURE_RETRY
+ TEMP_FAILURE_RETRY(((bar(foo() == 1)) == 1));
+ // CHECK-MESSAGES: :[[@LINE-1]]:41: warning: Top-level comparisons should be moved out of TEMP_FAILURE_RETRY
+ TEMP_FAILURE_RETRY((int)((bar(foo() == 1)) == 1));
+ // CHECK-MESSAGES: :[[@LINE-1]]:46: warning: Top-level comparisons should be moved out of TEMP_FAILURE_RETRY
+
+#define INDIRECT TEMP_FAILURE_RETRY
+ INDIRECT(foo());
+ INDIRECT((foo() == 1));
+ // CHECK-MESSAGES: :[[@LINE-1]]:19: warning: Top-level comparisons should be moved out of TEMP_FAILURE_RETRY
+ INDIRECT(bar(foo() == 1));
+ INDIRECT((int)((bar(foo() == 1)) == 1));
+ // CHECK-MESSAGES: :[[@LINE-1]]:36: warning: Top-level comparisons should be moved out of TEMP_FAILURE_RETRY
+
+#define TFR(x) TEMP_FAILURE_RETRY(x)
+ TFR(foo());
+ TFR((foo() == 1));
+ // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: Top-level comparisons should be moved out of TEMP_FAILURE_RETRY
+ TFR(bar(foo() == 1));
+ TFR((int)((bar(foo() == 1)) == 1));
+ // CHECK-MESSAGES: :[[@LINE-1]]:31: warning: Top-level comparisons should be moved out of TEMP_FAILURE_RETRY
+
+#define ADD_TFR(x) (1 + TEMP_FAILURE_RETRY(x) + 1)
+ ADD_TFR(foo());
+ ADD_TFR(foo() == 1);
+ // CHECK-MESSAGES: :[[@LINE-1]]:17: warning: Top-level comparisons should be moved out of TEMP_FAILURE_RETRY
+
+ ADD_TFR(bar(foo() == 1));
+ ADD_TFR((int)((bar(foo() == 1)) == 1));
+ // CHECK-MESSAGES: :[[@LINE-1]]:35: warning: Top-level comparisons should be moved out of TEMP_FAILURE_RETRY
+
+#define ADDP_TFR(x) (1 + TEMP_FAILURE_RETRY((x)) + 1)
+ ADDP_TFR(foo());
+ ADDP_TFR((foo() == 1));
+ // CHECK-MESSAGES: :[[@LINE-1]]:19: warning: Top-level comparisons should be moved out of TEMP_FAILURE_RETRY
+
+ ADDP_TFR(bar(foo() == 1));
+ ADDP_TFR((int)((bar(foo() == 1)) == 1));
+ // CHECK-MESSAGES: :[[@LINE-1]]:36: warning: Top-level comparisons should be moved out of TEMP_FAILURE_RETRY
+
+#define MACRO TEMP_FAILURE_RETRY(foo() == 1)
+ MACRO;
+ // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: Top-level comparisons should be moved out of TEMP_FAILURE_RETRY
+
+ // Be sure that being a macro arg doesn't mess with this.
+#define ID(x) (x)
+ ID(ADDP_TFR(bar(foo() == 1)));
+ ID(ADDP_TFR(bar(foo() == 1) == 1));
+ // CHECK-MESSAGES: :[[@LINE-1]]:31: warning: Top-level comparisons should be moved out of TEMP_FAILURE_RETRY
+ ID(MACRO);
+ // CHECK-MESSAGES: :[[@LINE-1]]:6: warning: Top-level comparisons should be moved out of TEMP_FAILURE_RETRY
+
+#define CMP(x) x == 1
+ TEMP_FAILURE_RETRY(CMP(foo()));
+ // CHECK-MESSAGES: :[[@LINE-1]]:22: warning: Top-level comparisons should be moved out of TEMP_FAILURE_RETRY
+}
+
+// I can't find a case where TEMP_FAILURE_RETRY is implemented like this, but if
+// we can cheaply support it, I don't see why not.
+void obscured_temp_failure_retry() {
+#undef TEMP_FAILURE_RETRY
+#define IMPL(x) \
+ ({ \
+ typeof(x) __z; \
+ do \
+ __z = (x); \
+ while (__z == -1); \
+ __z; \
+ })
+
+#define IMPL2(x) IMPL(x)
+#define TEMP_FAILURE_RETRY(x) IMPL2(x)
+ TEMP_FAILURE_RETRY((foo()));
+ TEMP_FAILURE_RETRY((int)(foo() == 1));
+ // CHECK-MESSAGES: :[[@LINE-1]]:34: warning: Top-level comparisons should be moved out of TEMP_FAILURE_RETRY
+ TEMP_FAILURE_RETRY((bar(foo() == 1)));
+ TEMP_FAILURE_RETRY((int)((bar(foo() == 1)) == 1));
+ // CHECK-MESSAGES: :[[@LINE-1]]:46: warning: Top-level comparisons should be moved out of TEMP_FAILURE_RETRY
+}
Index: docs/clang-tidy/checks/list.rst
===================================================================
--- docs/clang-tidy/checks/list.rst
+++ docs/clang-tidy/checks/list.rst
@@ -21,6 +21,7 @@
bugprone-argument-comment
bugprone-assert-side-effect
bugprone-bool-pointer-implicit-conversion
+ bugprone-comparison-in-temp-failure-retry
bugprone-copy-constructor-init
bugprone-dangling-handle
bugprone-fold-init-type
Index: docs/clang-tidy/checks/bugprone-comparison-in-temp-failure-retry.rst
===================================================================
--- /dev/null
+++ docs/clang-tidy/checks/bugprone-comparison-in-temp-failure-retry.rst
@@ -0,0 +1,30 @@
+.. title:: clang-tidy - bugprone-comparison-in-temp-failure-retry
+
+bugprone-comparison-in-temp-failure-retry
+=========================================
+
+Checks whether a use of ``TEMP_FAILURE_RETRY`` has a top-level comparison in its
+argument. Having such a use is incorrect in the vast majority of cases, and
+will often silently defeat the purpose of the ``TEMP_FAILURE_RETRY`` macro.
+
+Example buggy usage looks like:
+
+.. code-block:: c
+
+ char cs[1];
+ while (TEMP_FAILURE_RETRY(read(STDIN_FILENO, cs, sizeof(cs)) != 0)) {
+ // Do something with cs.
+ }
+
+Since TEMP_FAILURE_RETRY will check for whether the result *of the comparison*
+is ``-1``, and retry if so.
+
+If you encounter this, the fix is simple: lift the comparison out of the
+``TEMP_FAILURE_RETRY`` argument, like so:
+
+.. code-block:: c
+
+ char cs[1];
+ while (TEMP_FAILURE_RETRY(read(STDIN_FILENO, cs, sizeof(cs))) != 0) {
+ // Do something with cs.
+ }
Index: docs/ReleaseNotes.rst
===================================================================
--- docs/ReleaseNotes.rst
+++ docs/ReleaseNotes.rst
@@ -57,6 +57,12 @@
Improvements to clang-tidy
--------------------------
+- New `bugprone-comparison-in-temp-failure-retry
+ <http://clang.llvm.org/extra/clang-tidy/checks/bugprone-comparison-in-temp-failure-retry.html>`_ check
+
+ Diagnoses comparisons that appear to be incorrectly placed in the argument to
+ the `TEMP_FAILURE_RETRY` macro.
+
- New module ``portability``.
- New module ``zircon`` for checks related to Fuchsia's Zircon kernel.
Index: clang-tidy/bugprone/ComparisonInTempFailureRetryCheck.h
===================================================================
--- /dev/null
+++ clang-tidy/bugprone/ComparisonInTempFailureRetryCheck.h
@@ -0,0 +1,34 @@
+//===--- ComparisonInTempFailureRetryCheck.h - clang-tidy--------*- C++ -*-===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_COMPARISONINTEMPFAILURERETRYCHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_COMPARISONINTEMPFAILURERETRYCHECK_H
+
+#include "../ClangTidy.h"
+
+namespace clang {
+namespace tidy {
+namespace bugprone {
+
+/// Attempts to catch calls to TEMP_FAILURE_RETRY with a top-level comparison
+/// operation, like `TEMP_FAILURE_RETRY(read(...) != N)`. In these cases, the
+/// comparison should go outside of the TEMP_FAILURE_RETRY.
+class ComparisonInTempFailureRetryCheck : public ClangTidyCheck {
+public:
+ ComparisonInTempFailureRetryCheck(StringRef Name, ClangTidyContext *Context)
+ : ClangTidyCheck(Name, Context) {}
+ void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+ void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+};
+
+} // namespace bugprone
+} // namespace tidy
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_COMPARISONINTEMPFAILURERETRYCHECK_H
Index: clang-tidy/bugprone/ComparisonInTempFailureRetryCheck.cpp
===================================================================
--- /dev/null
+++ clang-tidy/bugprone/ComparisonInTempFailureRetryCheck.cpp
@@ -0,0 +1,85 @@
+//===--- ComparisonInTempFailureRetryCheck.cpp - clang-tidy----------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "ComparisonInTempFailureRetryCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Lexer.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+namespace bugprone {
+
+namespace {
+AST_MATCHER(Expr, isBinOpComparison) {
+ const auto *BinOp = dyn_cast<BinaryOperator>(Node.IgnoreParenCasts());
+ return BinOp && BinOp->isComparisonOp();
+}
+
+AST_MATCHER(BinaryOperator, isRHSATempFailureRetryArg) {
+ if (!Node.getLocStart().isMacroID())
+ return false;
+
+ const SourceManager &SM = Finder->getASTContext().getSourceManager();
+ if (!SM.isMacroArgExpansion(Node.getRHS()->IgnoreParenCasts()->getLocStart()))
+ return false;
+
+ const LangOptions &Opts = Finder->getASTContext().getLangOpts();
+ SourceLocation LocStart = Node.getLocStart();
+ while (LocStart.isMacroID()) {
+ SourceLocation Invocation = SM.getImmediateMacroCallerLoc(LocStart);
+ Token Tok;
+ if (!Lexer::getRawToken(SM.getSpellingLoc(Invocation), Tok, SM, Opts,
+ /*IgnoreWhiteSpace=*/true)) {
+ if (Tok.getKind() == tok::raw_identifier &&
+ Tok.getRawIdentifier() == "TEMP_FAILURE_RETRY")
+ return true;
+ }
+
+ LocStart = Invocation;
+ }
+ return false;
+}
+}
+
+
+void ComparisonInTempFailureRetryCheck::registerMatchers(MatchFinder *Finder) {
+ // Both glibc's and Bionic's TEMP_FAILURE_RETRY macros structurally look like:
+ //
+ // #define TEMP_FAILURE_RETRY(x) ({ \
+ // typeof(x) y; \
+ // do y = (x); \
+ // while (y == -1 && errno != EINTR); \
+ // y; \
+ // })
+ //
+ // It's unclear how to walk up the AST from inside the expansion of `x`, and
+ // we need to not complain about things like TEMP_FAILURE_RETRY(foo(x == 1)),
+ // so we just match the assignment of `y = (x)` and inspect `x` from there.
+ Finder->addMatcher(binaryOperator(hasOperatorName("="),
+ hasRHS(isBinOpComparison()),
+ isRHSATempFailureRetryArg())
+ .bind("assign"),
+ this);
+}
+
+void ComparisonInTempFailureRetryCheck::check(const MatchFinder::MatchResult &Result) {
+ const auto &Assign = *Result.Nodes.getNodeAs<BinaryOperator>("assign");
+ const auto &RHS = *cast<BinaryOperator>(Assign.getRHS()->IgnoreParenCasts());
+ assert(RHS.isComparisonOp());
+
+ diag(RHS.getOperatorLoc(),
+ "Top-level comparisons should be moved out of TEMP_FAILURE_RETRY");
+}
+
+} // namespace bugprone
+} // namespace tidy
+} // namespace clang
Index: clang-tidy/bugprone/CMakeLists.txt
===================================================================
--- clang-tidy/bugprone/CMakeLists.txt
+++ clang-tidy/bugprone/CMakeLists.txt
@@ -5,6 +5,7 @@
AssertSideEffectCheck.cpp
BoolPointerImplicitConversionCheck.cpp
BugproneTidyModule.cpp
+ ComparisonInTempFailureRetryCheck.cpp
CopyConstructorInitCheck.cpp
DanglingHandleCheck.cpp
FoldInitTypeCheck.cpp
Index: clang-tidy/bugprone/BugproneTidyModule.cpp
===================================================================
--- clang-tidy/bugprone/BugproneTidyModule.cpp
+++ clang-tidy/bugprone/BugproneTidyModule.cpp
@@ -13,6 +13,7 @@
#include "ArgumentCommentCheck.h"
#include "AssertSideEffectCheck.h"
#include "BoolPointerImplicitConversionCheck.h"
+#include "ComparisonInTempFailureRetryCheck.h"
#include "CopyConstructorInitCheck.h"
#include "DanglingHandleCheck.h"
#include "FoldInitTypeCheck.h"
@@ -60,6 +61,8 @@
"bugprone-assert-side-effect");
CheckFactories.registerCheck<BoolPointerImplicitConversionCheck>(
"bugprone-bool-pointer-implicit-conversion");
+ CheckFactories.registerCheck<ComparisonInTempFailureRetryCheck>(
+ "bugprone-comparison-in-temp-failure-retry");
CheckFactories.registerCheck<CopyConstructorInitCheck>(
"bugprone-copy-constructor-init");
CheckFactories.registerCheck<DanglingHandleCheck>(
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