[Sema] Add a new warning, -Wmemset-transposed-args

This diagnoses calls to memset that have the second and third arguments
transposed, for example:

  memset(buf, sizeof(buf), 0);

This is done by checking if the third argument is a literal 0, or if the second
is a sizeof expression (and the third isn't). The first check is also done for
calls to bzero.

Differential revision: https://reviews.llvm.org/D49112

llvm-svn: 337470

1 files changed, 60 insertions, 0 deletions

diff --git a/clang/test/Sema/transpose-memset.c b/clang/test/Sema/transpose-memset.c
new file mode 100644
index 00000000000..0180d5051e5
--- /dev/null
+++ b/clang/test/Sema/transpose-memset.c
@@ -0,0 +1,60 @@
+// RUN: %clang_cc1       -Wmemset-transposed-args -verify %s
+// RUN: %clang_cc1 -xc++ -Wmemset-transposed-args -verify %s
+
+#define memset(...) __builtin_memset(__VA_ARGS__)
+#define bzero(x,y) __builtin_memset(x, 0, y)
+#define real_bzero(x,y) __builtin_bzero(x,y)
+
+int array[10];
+int *ptr;
+
+int main() {
+  memset(array, sizeof(array), 0); // expected-warning{{'size' argument to memset is '0'; did you mean to transpose the last two arguments?}} expected-note{{parenthesize the third argument to silence}}
+  memset(array, sizeof(array), 0xff); // expected-warning{{setting buffer to a 'sizeof' expression; did you mean to transpose the last two arguments?}} expected-note{{cast the second argument to 'int' to silence}}
+  memset(ptr, sizeof(ptr), 0); // expected-warning{{'size' argument to memset is '0'; did you mean to transpose the last two arguments?}} expected-note{{parenthesize the third argument to silence}}
+  memset(ptr, sizeof(*ptr) * 10, 1); // expected-warning{{setting buffer to a 'sizeof' expression; did you mean to transpose the last two arguments?}} expected-note{{cast the second argument to 'int' to silence}}
+  memset(ptr, 10 * sizeof(int *), 1); // expected-warning{{setting buffer to a 'sizeof' expression; did you mean to transpose the last two arguments?}} expected-note{{cast the second argument to 'int' to silence}}
+  memset(ptr, 10 * sizeof(int *) + 10, 0xff); // expected-warning{{setting buffer to a 'sizeof' expression; did you mean to transpose the last two arguments?}} expected-note{{cast the second argument to 'int' to silence}}
+  memset(ptr, sizeof(char) * sizeof(int *), 0xff); // expected-warning{{setting buffer to a 'sizeof' expression; did you mean to transpose the last two arguments?}} expected-note{{cast the second argument to 'int' to silence}}
+  memset(array, sizeof(array), sizeof(array)); // Uh... fine I guess.
+  memset(array, 0, sizeof(array));
+  memset(ptr, 0, sizeof(int *) * 10);
+  memset(array, (int)sizeof(array), (0)); // no warning
+  memset(array, (int)sizeof(array), 32); // no warning
+  memset(array, 32, (0)); // no warning
+
+  bzero(ptr, 0); // expected-warning{{'size' argument to bzero is '0'}} expected-note{{parenthesize the second argument to silence}}
+  real_bzero(ptr, 0); // expected-warning{{'size' argument to bzero is '0'}} expected-note{{parenthesize the second argument to silence}}
+}
+
+void macros() {
+#define ZERO 0
+  int array[10];
+  memset(array, 0xff, ZERO); // no warning
+  // Still emit a diagnostic for memsetting a sizeof expression:
+  memset(array, sizeof(array), ZERO); // expected-warning{{'sizeof'}} expected-note{{cast}}
+  bzero(array, ZERO); // no warning
+  real_bzero(array, ZERO); // no warning
+#define NESTED_DONT_DIAG                        \
+  memset(array, 0xff, ZERO);                    \
+  real_bzero(array, ZERO);
+
+  NESTED_DONT_DIAG;
+
+#define NESTED_DO_DIAG                          \
+  memset(array, 0xff, 0);                       \
+  real_bzero(array, 0)
+
+  NESTED_DO_DIAG; // expected-warning{{'size' argument to memset}} expected-warning{{'size' argument to bzero}} expected-note2{{parenthesize}}
+
+#define FN_MACRO(p)                             \
+  memset(array, 0xff, p)
+
+  FN_MACRO(ZERO);
+  FN_MACRO(0); // FIXME: should we diagnose this?
+
+  __builtin_memset(array, 0, ZERO); // no warning
+  __builtin_bzero(array, ZERO);
+  __builtin_memset(array, 0, 0); // expected-warning{{'size' argument to memset}} // expected-note{{parenthesize}}
+  __builtin_bzero(array, 0); // expected-warning{{'size' argument to bzero}} // expected-note{{parenthesize}}
+}