Add a C++ wrapper for GCC C plug-in

This patch introduces a new class which wraps the GCC C compile plug-in.
It is a little unfortunate that this all happened in between the time that
GCC moved to C++ and GDB moved to C++, leaving us with an ABI promise to
support a C-like interface.  The hope is to isolate GDB from some of this
should it change in the future.

Broadly, what this does is replace calls like:

  C_CTX (context)->c_ops->operation (C_CTX (context), ...);

with calls that now look like:

  context->c_plugin->operation (...);

This API will be further refined in following patches when struct
compile_instance/compile_c_instance are changed into classes.

gdb/ChangeLog:
        * Makefile.in (HFILES_NO_SRCDIR): Add compile/gcc-c-plugin.h.
        * compile/compile-c-types.c: Define GCC_METHODN macros and include
        gcc-c-fe.def to define C plugin.
        (delete_instance): Delete `c_plugin'.
        (new_compile_instance): Initialize `c_plugin'.
        * compile/compile-c.h: Include gcc_c_plugin.h.
        (struct compile_c_instance) <c_plugin>: New member.
        * gcc-c-plugin.h: New file.
        Update all callers with API change.

1 files changed, 4 insertions, 5 deletions

diff --git a/gdb/compile/compile-c.h b/gdb/compile/compile-c.h
index cff2aef..ffa5802 100644
--- a/gdb/compile/compile-c.h
+++ b/gdb/compile/compile-c.h
@@ -18,6 +18,7 @@
 #define GDB_COMPILE_C_H
 
 #include "common/enum-flags.h"
+#include "gcc-c-plugin.h"
 #include "hashtab.h"
 
 /* enum-flags wrapper.  */
@@ -46,12 +47,10 @@ struct compile_c_instance
 
   /* Map from gdb symbols to gcc error messages to emit.  */
   htab_t symbol_err_map;
-};
-
-/* A helper macro that takes a compile_c_instance and returns its
-   corresponding gcc_c_context.  */
 
-#define C_CTX(I) ((struct gcc_c_context *) ((I)->base.fe))
+  /* GCC C plugin.  */
+  gcc_c_plugin *c_plugin;
+};
 
 /* Emit code to compute the address for all the local variables in
    scope at PC in BLOCK.  Returns a malloc'd vector, indexed by gdb