We've been burnt by this issue repeatedly (cf c2d1eea9e, d025cf88b,
11b500072) so I think it's time to try to formalize and document
what to do to export a variable from src/common/ or src/port/.
Here's a draft patch. I'm not in love with the name "PGDLLIMPORT_FE"
and would welcome better ideas.
regards, tom lane
diff --git a/src/include/c.h b/src/include/c.h
index c8ede08273..e124e02d62 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -1312,10 +1312,34 @@ extern long long strtoll(const char *str, char **endptr, int base);
extern unsigned long long strtoull(const char *str, char **endptr, int base);
#endif
-/* no special DLL markers on most ports */
+/*
+ * Use "extern PGDLLIMPORT ..." to declare variables that are defined in
+ * the core backend and need to be accessible by loadable modules.
+ * No special marking is required on most ports.
+ */
#ifndef PGDLLIMPORT
#define PGDLLIMPORT
#endif
+
+/*
+ * Use "extern PGDLLIMPORT_FE ..." to declare variables that are defined in
+ * common frontend/backend libraries (src/common/ or src/port/). In the
+ * server, these are defined in the core backend and need to be accessible by
+ * loadable modules. In frontend programs, these are defined locally and need
+ * no marking. In any case, no special marking is required on most ports.
+ */
+#ifndef FRONTEND
+#define PGDLLIMPORT_FE PGDLLIMPORT
+#else
+#define PGDLLIMPORT_FE
+#endif
+
+/*
+ * Use "extern PGDLLEXPORT ..." to declare functions that are defined in
+ * loadable modules and need to be callable by the core backend. Usually,
+ * this is not necessary because our build process automatically exports
+ * such symbols.
+ */
#ifndef PGDLLEXPORT
#define PGDLLEXPORT
#endif
diff --git a/src/include/common/keywords.h b/src/include/common/keywords.h
index 19e4eda8f9..54e40ac66c 100644
--- a/src/include/common/keywords.h
+++ b/src/include/common/keywords.h
@@ -22,14 +22,8 @@
#define TYPE_FUNC_NAME_KEYWORD 2
#define RESERVED_KEYWORD 3
-#ifndef FRONTEND
-extern PGDLLIMPORT const ScanKeywordList ScanKeywords;
-extern PGDLLIMPORT const uint8 ScanKeywordCategories[];
-extern PGDLLIMPORT const bool ScanKeywordBareLabel[];
-#else
-extern const ScanKeywordList ScanKeywords;
-extern const uint8 ScanKeywordCategories[];
-extern const bool ScanKeywordBareLabel[];
-#endif
+extern PGDLLIMPORT_FE const ScanKeywordList ScanKeywords;
+extern PGDLLIMPORT_FE const uint8 ScanKeywordCategories[];
+extern PGDLLIMPORT_FE const bool ScanKeywordBareLabel[];
#endif /* KEYWORDS_H */
diff --git a/src/include/common/pg_prng.h b/src/include/common/pg_prng.h
index e4df5165d7..a07214fd11 100644
--- a/src/include/common/pg_prng.h
+++ b/src/include/common/pg_prng.h
@@ -26,11 +26,7 @@ typedef struct pg_prng_state
* Callers not needing local PRNG series may use this global state vector,
* after initializing it with one of the pg_prng_...seed functions.
*/
-#ifndef FRONTEND
-extern PGDLLIMPORT pg_prng_state pg_global_prng_state;
-#else
-extern pg_prng_state pg_global_prng_state;
-#endif
+extern PGDLLIMPORT_FE pg_prng_state pg_global_prng_state;
extern void pg_prng_seed(pg_prng_state *state, uint64 seed);
extern void pg_prng_fseed(pg_prng_state *state, double fseed);
diff --git a/src/include/port/pg_bitutils.h b/src/include/port/pg_bitutils.h
index 7dd7fef4f7..0cdbfe7a14 100644
--- a/src/include/port/pg_bitutils.h
+++ b/src/include/port/pg_bitutils.h
@@ -13,15 +13,9 @@
#ifndef PG_BITUTILS_H
#define PG_BITUTILS_H
-#ifndef FRONTEND
-extern PGDLLIMPORT const uint8 pg_leftmost_one_pos[256];
-extern PGDLLIMPORT const uint8 pg_rightmost_one_pos[256];
-extern PGDLLIMPORT const uint8 pg_number_of_ones[256];
-#else
-extern const uint8 pg_leftmost_one_pos[256];
-extern const uint8 pg_rightmost_one_pos[256];
-extern const uint8 pg_number_of_ones[256];
-#endif
+extern PGDLLIMPORT_FE const uint8 pg_leftmost_one_pos[256];
+extern PGDLLIMPORT_FE const uint8 pg_rightmost_one_pos[256];
+extern PGDLLIMPORT_FE const uint8 pg_number_of_ones[256];
/*
* pg_leftmost_one_pos32
