From 667a9dbcb448738795bc9f51429160d8aed94b5c Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <peter@eisentraut.org>
Date: Wed, 28 Oct 2026 08:55:50 +0100
Subject: [PATCH v2 2/2] squash! Add compiler option -fstrict-flex-arrays=1

Also provide an attribute macro pg_attribute_strict_flex_array that
allows overriding the strict flex array level for a particular struct.
Use that to annotate WordEntryPosVector1.  Note that clang supports
the command-line option but not the attribute, so we can only use this
to optionally raise the level for some structs, but we can't do the
opposite of having a higher global level and lower it for some
exceptions.

Discussion: https://www.postgresql.org/message-id/flat/c79da9e1-965d-4530-9e3e-84b8bde134ec%40eisentraut.org
---
 src/include/c.h               | 19 +++++++++++++++++++
 src/include/tsearch/ts_type.h |  2 +-
 src/tools/pgindent/pgindent   |  1 +
 3 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/src/include/c.h b/src/include/c.h
index b285755e8c4..944c851b3c3 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -319,6 +319,25 @@ extern "C++"
 #define pg_attribute_returns_nonnull
 #endif
 
+/*
+ * pg_attribute_strict_flex_array(N) overrides -fstrict-flex-arrays=N for a
+ * particular struct field.  It can be used for example to annotate genuine
+ * trailing one-element array fields, which would under -fstrict-flex-arrays=1
+ * otherwise be considered flexible array members and be excluded from bounds
+ * checking.  Use pg_attribute_strict_flex_array(3) for such a case.
+ *
+ * Note that it is possible that the command-line option is supported but not
+ * the attribute.  To stay on the safe side, the attribute should not set a
+ * lower level than the global setting given by the command-line option.
+ *
+ * https://gcc.gnu.org/onlinedocs/gcc/Common-Attributes.html#index-strict_005fflex_005farray
+ */
+#if __has_attribute (strict_flex_array)
+#define pg_attribute_strict_flex_array(N) __attribute__((strict_flex_array(N)))
+#else
+#define pg_attribute_strict_flex_array(N)
+#endif
+
 /*
  * pg_attribute_target allows specifying different target options that the
  * function should be compiled with (e.g., for using special CPU instructions).
diff --git a/src/include/tsearch/ts_type.h b/src/include/tsearch/ts_type.h
index 345a2dab930..fdec91fdf13 100644
--- a/src/include/tsearch/ts_type.h
+++ b/src/include/tsearch/ts_type.h
@@ -76,7 +76,7 @@ typedef struct
 typedef struct
 {
 	uint16		npos;
-	WordEntryPos pos[1];
+	pg_attribute_strict_flex_array(3) WordEntryPos pos[1];
 } WordEntryPosVector1;
 
 #define MAXNUMPOS	(256)		/* semi-arbitrary limit on npos */
diff --git a/src/tools/pgindent/pgindent b/src/tools/pgindent/pgindent
index fa2041dc34b..f75c006bbff 100755
--- a/src/tools/pgindent/pgindent
+++ b/src/tools/pgindent/pgindent
@@ -253,6 +253,7 @@ sub write_source
 my @declaration_attributes = qw(
   alignas
   pg_attribute_counted_by
+  pg_attribute_strict_flex_array
 );
 
 # Text of each declaration attribute, stashed by pre_indent() and restored
-- 
2.56.0