[clang-tidy] readability-non-const-parameter: add new check that warns when function parameters should be const

The check will warn when the constness will make the function interface safer.

Reviewers: alexfh

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D15332

llvm-svn: 279507

1 files changed, 279 insertions, 0 deletions

diff --git a/clang-tools-extra/test/clang-tidy/readability-non-const-parameter.cpp b/clang-tools-extra/test/clang-tidy/readability-non-const-parameter.cpp
new file mode 100644
index 00000000000..4b1896cfdfd
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/readability-non-const-parameter.cpp
@@ -0,0 +1,279 @@
+// RUN: %check_clang_tidy %s readability-non-const-parameter %t
+
+// Currently the checker only warns about pointer arguments.
+//
+// It can be defined both that the data is const and that the pointer is const,
+// the checker only checks if the data can be const-specified.
+//
+// It does not warn about pointers to records or function pointers.
+
+// Some external function where first argument is nonconst and second is const.
+char *strcpy1(char *dest, const char *src);
+unsigned my_strcpy(char *buf, const char *s);
+unsigned my_strlen(const char *buf);
+
+// CHECK-MESSAGES: :[[@LINE+1]]:29: warning: pointer parameter 'last' can be pointer to const [readability-non-const-parameter]
+void warn1(int *first, int *last) {
+  // CHECK-FIXES: {{^}}void warn1(int *first, const int *last) {{{$}}
+  *first = 0;
+  if (first < last) {
+  } // <- last can be const
+}
+
+// TODO: warning should be written here
+void warn2(char *p) {
+  char buf[10];
+  strcpy1(buf, p);
+}
+
+// CHECK-MESSAGES: :[[@LINE+1]]:19: warning: pointer parameter 'p' can be
+void assign1(int *p) {
+  // CHECK-FIXES: {{^}}void assign1(const int *p) {{{$}}
+  const int *q;
+  q = p;
+}
+
+// CHECK-MESSAGES: :[[@LINE+1]]:19: warning: pointer parameter 'p' can be
+void assign2(int *p) {
+  // CHECK-FIXES: {{^}}void assign2(const int *p) {{{$}}
+  const int *q;
+  q = p + 1;
+}
+
+void assign3(int *p) {
+  *p = 0;
+}
+
+void assign4(int *p) {
+  *p += 2;
+}
+
+void assign5(char *p) {
+  p[0] = 0;
+}
+
+void assign6(int *p) {
+  int *q;
+  q = p++;
+}
+
+void assign7(char *p) {
+  char *a, *b;
+  a = b = p;
+}
+
+void assign8(char *a, char *b) {
+  char *x;
+  x = (a ? a : b);
+}
+
+void assign9(unsigned char *str, const unsigned int i) {
+  unsigned char *p;
+  for (p = str + i; *p;) {
+  }
+}
+
+void assign10(int *buf) {
+  int i, *p;
+  for (i = 0, p = buf; i < 10; i++, p++) {
+    *p = 1;
+  }
+}
+
+// CHECK-MESSAGES: :[[@LINE+1]]:17: warning: pointer parameter 'p' can be
+void init1(int *p) {
+  // CHECK-FIXES: {{^}}void init1(const int *p) {{{$}}
+  const int *q = p;
+}
+
+// CHECK-MESSAGES: :[[@LINE+1]]:17: warning: pointer parameter 'p' can be
+void init2(int *p) {
+  // CHECK-FIXES: {{^}}void init2(const int *p) {{{$}}
+  const int *q = p + 1;
+}
+
+void init3(int *p) {
+  int *q = p;
+}
+
+void init4(float *p) {
+  int *q = (int *)p;
+}
+
+void init5(int *p) {
+  int *i = p ? p : 0;
+}
+
+void init6(int *p) {
+  int *a[] = {p, p, 0};
+}
+
+void init7(int *p, int x) {
+  for (int *q = p + x - 1; 0; q++)
+    ;
+}
+
+// CHECK-MESSAGES: :[[@LINE+1]]:18: warning: pointer parameter 'p' can be
+int return1(int *p) {
+  // CHECK-FIXES: {{^}}int return1(const int *p) {{{$}}
+  return *p;
+}
+
+// CHECK-MESSAGES: :[[@LINE+1]]:25: warning: pointer parameter 'p' can be
+const int *return2(int *p) {
+  // CHECK-FIXES: {{^}}const int *return2(const int *p) {{{$}}
+  return p;
+}
+
+// CHECK-MESSAGES: :[[@LINE+1]]:25: warning: pointer parameter 'p' can be
+const int *return3(int *p) {
+  // CHECK-FIXES: {{^}}const int *return3(const int *p) {{{$}}
+  return p + 1;
+}
+
+// CHECK-MESSAGES: :[[@LINE+1]]:27: warning: pointer parameter 'p' can be
+const char *return4(char *p) {
+  // CHECK-FIXES: {{^}}const char *return4(const char *p) {{{$}}
+  return p ? p : "";
+}
+
+char *return5(char *s) {
+  return s;
+}
+
+char *return6(char *s) {
+  return s + 1;
+}
+
+char *return7(char *a, char *b) {
+  return a ? a : b;
+}
+
+char return8(int *p) {
+  return ++(*p);
+}
+
+void dontwarn1(int *p) {
+  ++(*p);
+}
+
+void dontwarn2(int *p) {
+  (*p)++;
+}
+
+int dontwarn3(_Atomic(int) * p) {
+  return *p;
+}
+
+void callFunction1(char *p) {
+  strcpy1(p, "abc");
+}
+
+void callFunction2(char *p) {
+  strcpy1(&p[0], "abc");
+}
+
+void callFunction3(char *p) {
+  strcpy1(p + 2, "abc");
+}
+
+char *callFunction4(char *p) {
+  return strcpy1(p, "abc");
+}
+
+unsigned callFunction5(char *buf) {
+  unsigned len = my_strlen(buf);
+  return len + my_strcpy(buf, "abc");
+}
+
+void f6(int **p);
+void callFunction6(int *p) { f6(&p); }
+
+typedef union { void *v; } t;
+void f7(t obj);
+void callFunction7(int *p) {
+  f7((t){p});
+}
+
+void f8(int &x);
+void callFunction8(int *p) {
+  f8(*p);
+}
+
+// Don't warn about nonconst function pointers that can be const.
+void functionpointer(double f(double), int x) {
+  f(x);
+}
+
+// TODO: This is a false positive.
+// CHECK-MESSAGES: :[[@LINE+1]]:27: warning: pointer parameter 'p' can be
+int functionpointer2(int *p) {
+  return *p;
+}
+void use_functionpointer2() {
+  int (*fp)(int *) = functionpointer2; // <- the parameter 'p' can't be const
+}
+
+// Don't warn about nonconst record pointers that can be const.
+struct XY {
+  int *x;
+  int *y;
+};
+void recordpointer(struct XY *xy) {
+  *(xy->x) = 0;
+}
+
+class C {
+public:
+  C(int *p) : p(p) {}
+
+private:
+  int *p;
+};
+
+class C2 {
+public:
+  // CHECK-MESSAGES: :[[@LINE+1]]:11: warning: pointer parameter 'p' can be
+  C2(int *p) : p(p) {}
+  // CHECK-FIXES: {{^}}  C2(const int *p) : p(p) {}{{$}}
+
+private:
+  const int *p;
+};
+
+void tempObject(int *p) {
+  C c(p);
+}
+
+// avoid fp for const pointer array
+void constPointerArray(const char *remapped[][2]) {
+  const char *name = remapped[0][0];
+}
+
+class Warn {
+public:
+  // CHECK-MESSAGES: :[[@LINE+1]]:21: warning: pointer parameter 'p' can be
+  void doStuff(int *p) {
+    // CHECK-FIXES: {{^}}  void doStuff(const int *p) {{{$}}
+    x = *p;
+  }
+
+private:
+  int x;
+};
+
+class Base {
+public:
+  // Ensure there is no false positive for this method. It is virtual.
+  virtual void doStuff(int *p) {
+    int x = *p;
+  }
+};
+
+class Derived : public Base {
+public:
+  // Ensure there is no false positive for this method. It overrides a method.
+  void doStuff(int *p) override {
+    int x = *p;
+  }
+};