Re: Mostly Harmless: c++bookends - patch 2 of 4

(Re-sending just the second of four patches: c++bookends)

These patches are based on CVS head in which the latest commit was
  user:        petere
  date:        Thu Dec 04 17:51:28 2008 +0000
  summary:     Default values for function arguments

2. c++bookends

     C++ code can call C functions and share global variables with C,
     provided those declarations are surrounded by "bookends":

         extern "C" {
         ...
         };

     Header files can be made bilingual, to declare interfaces which
     look the same to both C and C++ callers.  This is done by
     placing C++ bookends within the header file, guarded by #ifdefs

         #ifdef __cplusplus
         extern "C" {
         #endif
         ...
         #ifdef __cplusplus
         }; /* extern "C" */
         #endif

     This way the C++ caller can just #include the header file without
     worrying whether the interface is implemented in C or C++.

     Usually, extension modules written in C++ will put bookends around
     all of their PostgreSQL #includes.

     However, "postgres.h" usually stands alone as the first #include,
     followed by some system #includes, and then the rest of the
     PostgreSQL #includes.  It is much nicer if a C++ file has just one
     pair of bookends around its main block of PostgreSQL #includes.
     This patch gives postgres.h its own internal bookends, making it
     bilingual, so that its #include can continue to stand alone at the
     head of each file.

     Just a few additional header files are mentioned in the PostgreSQL
     Reference Manual for add-on developers to use: fmgr.h, funcapi.h,
     and spi.h.  This patch adds bookends within those three files for
     the benefit of beginners writing very simple extensions in C++.
     Documentation and learning are simplified because C example code
     can be compiled as C or C++ without change.

diff -r 55d732d0fbcd src/include/executor/spi.h
--- a/src/include/executor/spi.h
+++ b/src/include/executor/spi.h
@@ -18,6 +18,10 @@
  * included postgres.h
  */
 #include "postgres.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif

 /*
  *    Most of these are not needed by this file, but may be used by
@@ -156,4 +160,8 @@
 extern void AtEOXact_SPI(bool isCommit);
 extern void AtEOSubXact_SPI(bool isCommit, SubTransactionId mySubid);

+#ifdef __cplusplus
+}   /* extern "C" */
+#endif
+
 #endif   /* SPI_H */
diff -r 55d732d0fbcd src/include/fmgr.h
--- a/src/include/fmgr.h
+++ b/src/include/fmgr.h
@@ -17,6 +17,10 @@
  */
 #ifndef FMGR_H
 #define FMGR_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif

 /* We don't want to include primnodes.h here, so make a stub reference */
 typedef struct Node *fmNodePtr;
@@ -544,4 +548,8 @@
  */
 extern char *fmgr(Oid procedureId,...);

+#ifdef __cplusplus
+}   /* extern "C" */
+#endif
+
 #endif   /* FMGR_H */
diff -r 55d732d0fbcd src/include/funcapi.h
--- a/src/include/funcapi.h
+++ b/src/include/funcapi.h
@@ -16,11 +16,14 @@
 #ifndef FUNCAPI_H
 #define FUNCAPI_H

+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #include "fmgr.h"
 #include "access/tupdesc.h"
 #include "executor/executor.h"
 #include "executor/tuptable.h"
-

 /*-------------------------------------------------------------------------
  *    Support to ease writing Functions returning composite types
@@ -299,4 +302,8 @@
         PG_RETURN_NULL(); \
     } while (0)

+#ifdef __cplusplus
+}   /* extern "C" */
+#endif
+
 #endif   /* FUNCAPI_H */
diff -r 55d732d0fbcd src/include/postgres.h
--- a/src/include/postgres.h
+++ b/src/include/postgres.h
@@ -44,7 +44,12 @@
 #ifndef POSTGRES_H
 #define POSTGRES_H

+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #include "c.h"
+
 #include "utils/elog.h"
 #include "utils/palloc.h"

@@ -693,4 +698,8 @@
                      const char *errorType,
                      const char *fileName, int lineNumber);

+#ifdef __cplusplus
+}   /* extern "C" */
+#endif
+
 #endif   /* POSTGRES_H */