[clang-tidy] fix PR36489 - respect deduced pointer types from auto as well

Summary:
The cppcoreguidelines-pro-bounds-pointer-arithmetic warns on all occassion where
pointer arithmetic is used, but does not check values where the pointer types
is deduced via `auto`. This patch adjusts this behaviour and solved
PR36489.
I accidentally commited a wrong patch, this Differential is meant to have a
correct revision description and code attached to it.
Because the patch was accepted by aaron.ballman already, i will just commit
it.
See https://reviews.llvm.org/D48717 for the old differntial (contains wrong
code from the mixup)

Subscribers: nemanjai, xazax.hun, kbarton, cfe-commits

Differential Revision: https://reviews.llvm.org/D49682

llvm-svn: 337716

2 files changed, 59 insertions, 2 deletions

diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsPointerArithmeticCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsPointerArithmeticCheck.cpp
index d664b6401ae..dfbb51bed12 100644
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsPointerArithmeticCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsPointerArithmeticCheck.cpp
@@ -21,12 +21,16 @@ void ProBoundsPointerArithmeticCheck::registerMatchers(MatchFinder *Finder) {
   if (!getLangOpts().CPlusPlus)
     return;
 
+  const auto AllPointerTypes = anyOf(
+      hasType(pointerType()), hasType(autoType(hasDeducedType(pointerType()))),
+      hasType(decltypeType(hasUnderlyingType(pointerType()))));
+
   // Flag all operators +, -, +=, -=, ++, -- that result in a pointer
   Finder->addMatcher(
       binaryOperator(
           anyOf(hasOperatorName("+"), hasOperatorName("-"),
                 hasOperatorName("+="), hasOperatorName("-=")),
-          hasType(pointerType()),
+          AllPointerTypes,
           unless(hasLHS(ignoringImpCasts(declRefExpr(to(isImplicit()))))))
           .bind("expr"),
       this);
@@ -41,7 +45,7 @@ void ProBoundsPointerArithmeticCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
       arraySubscriptExpr(
           hasBase(ignoringImpCasts(
-              anyOf(hasType(pointerType()),
+              anyOf(AllPointerTypes,
                     hasType(decayedType(hasDecayedType(pointerType())))))))
           .bind("expr"),
       this);
diff --git a/clang-tools-extra/test/clang-tidy/cppcoreguidelines-pro-bounds-pointer-arithmetic-pr36489.cpp b/clang-tools-extra/test/clang-tidy/cppcoreguidelines-pro-bounds-pointer-arithmetic-pr36489.cpp
new file mode 100644
index 00000000000..47109522667
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/cppcoreguidelines-pro-bounds-pointer-arithmetic-pr36489.cpp
@@ -0,0 +1,53 @@
+// RUN: %check_clang_tidy %s cppcoreguidelines-pro-bounds-pointer-arithmetic %t -- -- -std=c++14
+
+// Fix PR36489 and detect auto-deduced value correctly.
+char *getPtr();
+auto getPtrAuto() { return getPtr(); }
+decltype(getPtr()) getPtrDeclType();
+decltype(auto) getPtrDeclTypeAuto() { return getPtr(); }
+auto getPtrWithTrailingReturnType() -> char *;
+
+void auto_deduction_binary() {
+  auto p1 = getPtr() + 1;
+  // CHECK-MESSAGES: :[[@LINE-1]]:22: warning: do not use pointer arithmetic
+  auto p2 = getPtrAuto() + 1;
+  // CHECK-MESSAGES: :[[@LINE-1]]:26: warning: do not use pointer arithmetic
+  auto p3 = getPtrWithTrailingReturnType() + 1;
+  // CHECK-MESSAGES: :[[@LINE-1]]:44: warning: do not use pointer arithmetic
+  auto p4 = getPtr();
+  auto *p5 = getPtr();
+  p4 = p4 + 1;
+  // CHECK-MESSAGES: :[[@LINE-1]]:11: warning: do not use pointer arithmetic
+  p5 = p5 + 1;
+  // CHECK-MESSAGES: :[[@LINE-1]]:11: warning: do not use pointer arithmetic
+  auto p6 = getPtrDeclType() + 1;
+  // CHECK-MESSAGES: :[[@LINE-1]]:30: warning: do not use pointer arithmetic
+  auto p7 = getPtrDeclTypeAuto() + 1;
+  // CHECK-MESSAGES: :[[@LINE-1]]:34: warning: do not use pointer arithmetic
+  auto *p8 = getPtrDeclType() + 1;
+  // CHECK-MESSAGES: :[[@LINE-1]]:31: warning: do not use pointer arithmetic
+  auto *p9 = getPtrDeclTypeAuto() + 1;
+  // CHECK-MESSAGES: :[[@LINE-1]]:35: warning: do not use pointer arithmetic
+}
+
+void auto_deduction_subscript() {
+  char p1 = getPtr()[2];
+  // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: do not use pointer arithmetic
+  auto p2 = getPtr()[3];
+  // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: do not use pointer arithmetic
+
+  char p3 = getPtrAuto()[4];
+  // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: do not use pointer arithmetic
+  auto p4 = getPtrAuto()[5];
+  // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: do not use pointer arithmetic
+
+  char p5 = getPtrWithTrailingReturnType()[6];
+  // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: do not use pointer arithmetic
+  auto p6 = getPtrWithTrailingReturnType()[7];
+  // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: do not use pointer arithmetic
+
+  auto p7 = getPtrDeclType()[8];
+  // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: do not use pointer arithmetic
+  auto p8 = getPtrDeclTypeAuto()[9];
+  // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: do not use pointer arithmetic
+}