diagnostics missing from -Wc++-compat

[zygoloid]

Bugzilla Link	21524
Version	trunk
OS	Linux
CC	@DougGregor

Extended Description

From http://lists.cs.uiuc.edu/pipermail/cfe-dev/2014-November/039875.html

clang doesn't print warning for following test-case:

compiled with: clang -fsyntax-only -Wc++-compat

int new;
struct A
{
struct B
{
int x;
}bs;
int y;
};
struct B b;

gcc -fsyntax-only -Wc++-compat prints following warnings (gcc-4.9.1 ubuntu):

t.c:1:5: warning: identifier ‘new’ conflicts with C++ keyword [-Wc++-compat]
int new;
^
t.c:13:8: warning: struct defined in struct or union is not visible in
C++ [-Wc++-compat]
struct B b;
^
t.c:5:10: note: struct defined here
struct B
^

[llvmbot]

@llvm/issue-subscribers-c

Author: None (ec04fc15-fa35-46f2-80e1-5d271f2ef708)

| | | | --- | --- | | Bugzilla Link | [21524](https://llvm.org/bz21524) | | Version | trunk | | OS | Linux | | CC | @DougGregor |

Extended Description

From http://lists.cs.uiuc.edu/pipermail/cfe-dev/2014-November/039875.html

clang doesn't print warning for following test-case:

compiled with: clang -fsyntax-only -Wc++-compat

int new;
struct A
{
struct B
{
int x;
}bs;
int y;
};
struct B b;

gcc -fsyntax-only -Wc++-compat prints following warnings (gcc-4.9.1 ubuntu):

t.c:1:5: warning: identifier ‘new’ conflicts with C++ keyword [-Wc++-compat]
int new;
^
t.c:13:8: warning: struct defined in struct or union is not visible in
C++ [-Wc++-compat]
struct B b;
^
t.c:5:10: note: struct defined here
struct B
^

[wheatman]

This still exists in post 17 trunk(e68c265)

https://godbolt.org/z/fGcnGTrn5

code

int new;
struct A {
  struct B  { int x; } bs;
  int y;
};
struct B b;

clang gives no warnings with -Wc++-compat

on the other hand gcc gives the following warning

<source>:1:5: warning: identifier 'new' conflicts with C++ keyword [-Wc++-compat]
    1 | int new;
      |     ^~~
<source>:6:8: warning: struct defined in struct or union is not visible in C++ [-Wc++-compat]
    6 | struct B b;
      |        ^
<source>:3:10: note: struct defined here
    3 |   struct B  { int x; } bs;
      |          ^
Compiler returned: 0