Add -Wmissing-variable-declarations to the standard compilation flags

This warning flag detects global variables not declared in header
files.  This is similar to what -Wmissing-prototypes does for
functions.  (More correctly, it is similar to what
-Wmissing-declarations does for functions, but -Wmissing-prototypes is
a superset of that in C.)

This flag is new in GCC 14.  Clang has supported it for a while.

Several recent commits have cleaned up warnings triggered by this, so
it should now be clean.

Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://www.postgresql.org/message-id/flat/e0a62134-83da-4ba4-8cdb-ceb0111c95ce@eisentraut.org

6 files changed, 8 insertions, 1 deletions

diff --git a/src/Makefile.global.in b/src/Makefile.global.in
index 83b91fe9167..42f50b49761 100644
--- a/src/Makefile.global.in
+++ b/src/Makefile.global.in
@@ -266,6 +266,7 @@ CFLAGS_POPCNT = @CFLAGS_POPCNT@
 CFLAGS_CRC = @CFLAGS_CRC@
 CFLAGS_XSAVE = @CFLAGS_XSAVE@
 PERMIT_DECLARATION_AFTER_STATEMENT = @PERMIT_DECLARATION_AFTER_STATEMENT@
+PERMIT_MISSING_VARIABLE_DECLARATIONS = @PERMIT_MISSING_VARIABLE_DECLARATIONS@
 CXXFLAGS = @CXXFLAGS@
 
 LLVM_CPPFLAGS = @LLVM_CPPFLAGS@
diff --git a/src/interfaces/ecpg/test/Makefile.regress b/src/interfaces/ecpg/test/Makefile.regress
index b0647cd2c5f..9bf0efa40b9 100644
--- a/src/interfaces/ecpg/test/Makefile.regress
+++ b/src/interfaces/ecpg/test/Makefile.regress
@@ -3,7 +3,7 @@
 
 override CPPFLAGS := -I../../include -I$(top_srcdir)/src/interfaces/ecpg/include \
 	-I$(libpq_srcdir) $(CPPFLAGS)
-override CFLAGS += $(PTHREAD_CFLAGS)
+override CFLAGS += $(PTHREAD_CFLAGS) $(PERMIT_MISSING_VARIABLE_DECLARATIONS)
 
 LDFLAGS_INTERNAL += -L../../ecpglib -lecpg -L../../pgtypeslib -lpgtypes $(libpq)
 
diff --git a/src/interfaces/ecpg/test/meson.build b/src/interfaces/ecpg/test/meson.build
index c1e508ccc82..8fd284071f2 100644
--- a/src/interfaces/ecpg/test/meson.build
+++ b/src/interfaces/ecpg/test/meson.build
@@ -27,6 +27,7 @@ testprep_targets += pg_regress_ecpg
 
 # create .c files and executables from .pgc files
 ecpg_test_exec_kw = {
+  'c_args': cflags_no_missing_var_decls,
   'dependencies': [frontend_code, libpq],
   'include_directories': [ecpg_inc],
   'link_with': [ecpglib_so, ecpg_compat_so, ecpg_pgtypes_so],
diff --git a/src/makefiles/meson.build b/src/makefiles/meson.build
index 5618050b306..850e9275845 100644
--- a/src/makefiles/meson.build
+++ b/src/makefiles/meson.build
@@ -98,6 +98,8 @@ pgxs_kv = {
   'CXXFLAGS_SL_MODULE': ' '.join(cxxflags_mod),
   'PERMIT_DECLARATION_AFTER_STATEMENT':
     ' '.join(cflags_no_decl_after_statement),
+  'PERMIT_MISSING_VARIABLE_DECLARATIONS':
+    ' '.join(cflags_no_missing_var_decls),
 
   'CFLAGS_CRC': ' '.join(cflags_crc),
   'CFLAGS_POPCNT': ' '.join(cflags_popcnt),
diff --git a/src/tools/pg_bsd_indent/Makefile b/src/tools/pg_bsd_indent/Makefile
index d922013e40b..f721dfb0d19 100644
--- a/src/tools/pg_bsd_indent/Makefile
+++ b/src/tools/pg_bsd_indent/Makefile
@@ -25,6 +25,8 @@ OBJS = \
 	parse.o \
 	pr_comment.o
 
+$(OBJS): CFLAGS += $(PERMIT_MISSING_VARIABLE_DECLARATIONS)
+
 all: pg_bsd_indent
 
 pg_bsd_indent: $(OBJS) | submake-libpgport
diff --git a/src/tools/pg_bsd_indent/meson.build b/src/tools/pg_bsd_indent/meson.build
index 4387c47740e..87ed4292975 100644
--- a/src/tools/pg_bsd_indent/meson.build
+++ b/src/tools/pg_bsd_indent/meson.build
@@ -18,6 +18,7 @@ endif
 
 pg_bsd_indent = executable('pg_bsd_indent',
   pg_bsd_indent_sources,
+  c_args: cflags_no_missing_var_decls,
   dependencies: [frontend_code],
   include_directories: include_directories('.'),
   kwargs: default_bin_args + {