[PATCH] D33102: [clang] Implement -Wcast-qual for C++

[Roman Lebedev via Phabricator via cfe-commits]

lebedev.ri added a comment.

So i'm trying to analyze that stage2 warning.
The testcase //seems// to be: (autogenerated all the variants)

  void test_nop() {
    unsigned char **ptr1 = 0;
    void **ptr2 = (void **)ptr1;
  }
  void test_bad() {
    unsigned char **ptr1 = 0;
    const void **ptr2 = (const void **)ptr1; // expected-warning {{cast from 'unsigned char **' to 'const void **' must have all intermediate pointers const qualified to be safe}}
  }
  void test_good0() {
    unsigned char **ptr1 = 0;
    void *const *ptr2 = (void *const *)ptr1;
  }
  void test_good1() {
    unsigned char **ptr1 = 0;
    const void *const *ptr2 = (const void *const *)ptr1;
  }
  void test_good2() {
    unsigned char *const *ptr1 = 0;
    void *const *ptr2 = (void *const *)ptr1;
  }
  void test_good3() {
    unsigned char *const *ptr1 = 0;
    const void *const *ptr2 = (const void *const *)ptr1;
  }
  void test_good4() {
    const unsigned char **ptr1 = 0;
    const void **ptr2 = (const void **)ptr1;
  }
  void test_good5() {
    const unsigned char **ptr1 = 0;
    const void *const *ptr2 = (const void *const *)ptr1;
  }
  void test_good6() {
    const unsigned char *const *ptr1 = 0;
    const void *const *ptr2 = (const void *const *)ptr1;
  }

GCC does not warn about such code at all, clang in C mode does warn about only one combination:

  $ gcc -c /tmp/test.c -Wcast-qual
  $ echo $?
  0
  $ clang -c /tmp/test.c -Wcast-qual
  /tmp/test.c:7:38: warning: cast from 'unsigned char **' to 'const void **' must have all intermediate pointers const qualified to be safe [-Wcast-qual]
    const void **ptr2 = (const void **)ptr1; // expected-warning {{cast from 'unsigned char **' to 'const void **' must have all intermediate pointers const qualified to be safe}}
                                       ^
  1 warning generated.

David, you reviewed the original `-Wcast-qual` patch, does all that ^ make sense?

F3429854: gen.cpp <https://reviews.llvm.org/F3429854>


Repository:
  rL LLVM

https://reviews.llvm.org/D33102