Add optional parameter to PG_TRY() macros

This optional parameter can be specified in cases where there are nested
PG_TRY() statements within a function in order to stop the compiler from
issuing warnings about shadowed local variables when compiling with
-Wshadow.  The optional parameter is used as a suffix on the variable
names declared within the PG_TRY(), PG_CATCH(), PG_FINALLY() and
PG_END_TRY() macros.  The parameter, if specified, must be the same in
each component macro of the given PG_TRY() block.

This also adjusts the single case where we have nested PG_TRY() statements
to add a parameter to the inner-most PG_TRY().

This reduces the number of compiler warnings when compiling with
-Wshadow=compatible-local from 5 down to 1.

Author: David Rowley
Discussion: https://postgr.es/m/CAApHDvqWGMdB_pATeUqE=JCtNqNxObPOJ00jFEa2_sZ20j_Wvg@mail.gmail.com

diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index aa0081578788c6c3b2344566986dfff22017a3ab..247d0816ad819bae88d8d8191f651a83a2de6258 100644 (file)
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -1678,16 +1678,16 @@ ProcessUtilitySlow(ParseState *pstate,
                                 * command itself is queued, which is enough.
                                 */
                                EventTriggerInhibitCommandCollection();
-                               PG_TRY();
+                               PG_TRY(2);
                                {
                                        address = ExecRefreshMatView((RefreshMatViewStmt *) parsetree,
                                                                                                 queryString, params, qc);
                                }
-                               PG_FINALLY();
+                               PG_FINALLY(2);
                                {
                                        EventTriggerUndoInhibitCommandCollection();
                                }
-                               PG_END_TRY();
+                               PG_END_TRY(2);
                                break;
 
                        case T_CreateTrigStmt:

diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index 4dd9658a3cf3640d911823cd7eea1cf3ad2bb0d3..f107a818e818df64bdfa03dd74699f98d7df4a21 100644 (file)
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -310,39 +310,47 @@ extern PGDLLIMPORT ErrorContextCallback *error_context_stack;
  * pedantry; we have seen bugs from compilers improperly optimizing code
  * away when such a variable was not marked.  Beware that gcc's -Wclobbered
  * warnings are just about entirely useless for catching such oversights.
+ *
+ * Each of these macros accepts an optional argument which can be specified
+ * to apply a suffix to the variables declared within the macros.  This suffix
+ * can be used to avoid the compiler emitting warnings about shadowed
+ * variables when compiling with -Wshadow in situations where nested PG_TRY()
+ * statements are required.  The optional suffix may contain any character
+ * that's allowed in a variable name.  The suffix, if specified, must be the
+ * same within each component macro of the given PG_TRY() statement.
  *----------
  */
-#define PG_TRY()  \
+#define PG_TRY(...)  \
        do { \
-               sigjmp_buf *_save_exception_stack = PG_exception_stack; \
-               ErrorContextCallback *_save_context_stack = error_context_stack; \
-               sigjmp_buf _local_sigjmp_buf; \
-               bool _do_rethrow = false; \
-               if (sigsetjmp(_local_sigjmp_buf, 0) == 0) \
+               sigjmp_buf *_save_exception_stack##__VA_ARGS__ = PG_exception_stack; \
+               ErrorContextCallback *_save_context_stack##__VA_ARGS__ = error_context_stack; \
+               sigjmp_buf _local_sigjmp_buf##__VA_ARGS__; \
+               bool _do_rethrow##__VA_ARGS__ = false; \
+               if (sigsetjmp(_local_sigjmp_buf##__VA_ARGS__, 0) == 0) \
                { \
-                       PG_exception_stack = &_local_sigjmp_buf
+                       PG_exception_stack = &_local_sigjmp_buf##__VA_ARGS__
 
-#define PG_CATCH()     \
+#define PG_CATCH(...)  \
                } \
                else \
                { \
-                       PG_exception_stack = _save_exception_stack; \
-                       error_context_stack = _save_context_stack
+                       PG_exception_stack = _save_exception_stack##__VA_ARGS__; \
+                       error_context_stack = _save_context_stack##__VA_ARGS__
 
-#define PG_FINALLY() \
+#define PG_FINALLY(...) \
                } \
                else \
-                       _do_rethrow = true; \
+                       _do_rethrow##__VA_ARGS__ = true; \
                { \
-                       PG_exception_stack = _save_exception_stack; \
-                       error_context_stack = _save_context_stack
+                       PG_exception_stack = _save_exception_stack##__VA_ARGS__; \
+                       error_context_stack = _save_context_stack##__VA_ARGS__
 
-#define PG_END_TRY()  \
+#define PG_END_TRY(...)  \
                } \
-               if (_do_rethrow) \
+               if (_do_rethrow##__VA_ARGS__) \
                                PG_RE_THROW(); \
-               PG_exception_stack = _save_exception_stack; \
-               error_context_stack = _save_context_stack; \
+               PG_exception_stack = _save_exception_stack##__VA_ARGS__; \
+               error_context_stack = _save_context_stack##__VA_ARGS__; \
        } while (0)
 
 /*