[clang-tidy] implement check for goto

The usage of `goto` is discourage in C++ since forever. This check implements
a warning for every `goto`. Even though there are (rare) valid use cases for
`goto`, better high level constructs should be used.

`goto` is used sometimes in C programs to free resources at the end of 
functions in the case of errors. This pattern is better implemented with
RAII in C++.

Reviewers: aaron.ballman, alexfh, hokein

Reviewed By: aaron.ballman

Subscribers: lebedev.ri, jbcoe, Eugene.Zelenko, klimek, nemanjai, mgorny, xazax.hun, kbarton, cfe-commits

Differential Revision: https://reviews.llvm.org/D41815

llvm-svn: 322626

1 files changed, 139 insertions, 0 deletions

diff --git a/clang-tools-extra/test/clang-tidy/cppcoreguidelines-avoid-goto.cpp b/clang-tools-extra/test/clang-tidy/cppcoreguidelines-avoid-goto.cpp
new file mode 100644
index 00000000000..213947f3709
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/cppcoreguidelines-avoid-goto.cpp
@@ -0,0 +1,139 @@
+// RUN: %check_clang_tidy %s cppcoreguidelines-avoid-goto %t
+
+void noop() {}
+
+int main() {
+  noop();
+  goto jump_to_me;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: avoid using 'goto' for flow control
+  // CHECK-MESSAGES: [[@LINE+3]]:1: note: label defined here
+  noop();
+
+jump_to_me:;
+
+jump_backwards:;
+  noop();
+  goto jump_backwards;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: avoid using 'goto' for flow control
+  // CHECK-MESSAGES: [[@LINE-4]]:1: note: label defined here
+
+  goto jump_in_line;
+  ;
+jump_in_line:;
+  // CHECK-MESSAGES: [[@LINE-3]]:3: warning: avoid using 'goto' for flow control
+  // CHECK-MESSAGES: [[@LINE-2]]:1: note: label defined here
+
+  // Test the GNU extension https://gcc.gnu.org/onlinedocs/gcc/Labels-as-Values.html
+some_label:;
+  void *dynamic_label = &&some_label;
+
+  // FIXME: `IndirectGotoStmt` is not detected.
+  goto *dynamic_label;
+}
+
+void forward_jump_out_nested_loop() {
+  int array[] = {1, 2, 3, 4, 5};
+  for (int i = 0; i < 10; ++i) {
+    noop();
+    for (int j = 0; j < 10; ++j) {
+      noop();
+      if (i + j > 10)
+        goto early_exit1;
+    }
+    noop();
+  }
+
+  for (int i = 0; i < 10; ++i) {
+    noop();
+    while (true) {
+      noop();
+      if (i > 5)
+        goto early_exit1;
+    }
+    noop();
+  }
+
+  for (auto value : array) {
+    noop();
+    for (auto number : array) {
+      noop();
+      if (number == 5)
+        goto early_exit1;
+    }
+  }
+
+  do {
+    noop();
+    do {
+      noop();
+      goto early_exit1;
+    } while (true);
+  } while (true);
+
+  do {
+    for (auto number : array) {
+      noop();
+      if (number == 2)
+        goto early_exit1;
+    }
+  } while (true);
+
+  // Jumping further results in error, because the variable declaration would
+  // be skipped.
+early_exit1:;
+
+  int i = 0;
+  while (true) {
+    noop();
+    while (true) {
+      noop();
+      if (i > 5)
+        goto early_exit2;
+      i++;
+    }
+    noop();
+  }
+
+  while (true) {
+    noop();
+    for (int j = 0; j < 10; ++j) {
+      noop();
+      if (j > 5)
+        goto early_exit2;
+    }
+    noop();
+  }
+
+  while (true) {
+    noop();
+    for (auto number : array) {
+      if (number == 1)
+        goto early_exit2;
+      noop();
+    }
+  }
+
+  while (true) {
+    noop();
+    do {
+      noop();
+      goto early_exit2;
+    } while (true);
+  }
+early_exit2:;
+}
+
+void jump_out_backwards() {
+
+before_the_loop:
+  noop();
+
+  for (int i = 0; i < 10; ++i) {
+    for (int j = 0; j < 10; ++j) {
+      if (i * j > 80)
+        goto before_the_loop;
+      // CHECK-MESSAGES: [[@LINE-1]]:9: warning: avoid using 'goto' for flow control
+      // CHECK-MESSAGES: [[@LINE-8]]:1: note: label defined here
+    }
+  }
+}