Convert src/tools/testint128.c into a test module.

This creates a new test module src/test/modules/test_int128 and moves
src/tools/testint128.c into it so that it can be built using the
normal build system, allowing the 128-bit integer arithmetic functions
in src/include/common/int128.h to be tested automatically. For now,
the tests are skipped on platforms that don't have native int128
support.

While at it, fix the test128 union in the test code: the "hl" member
of test128 was incorrectly defined to be a union instead of a struct,
which meant that the tests were only ever setting and checking half of
each 128-bit integer value.

Author: Dean Rasheed <dean.a.rasheed@gmail.com>
Reviewed-by: John Naylor <johncnaylorls@gmail.com>
Discussion: https://postgr.es/m/CAEZATCWgBMc9ZwKMYqQpaQz2X6gaamYRB+RnMsUNcdMcL2Mj_w@mail.gmail.com

src/test/modules/Makefile

@@ -25,6 +25,7 @@ SUBDIRS = \
 		  test_escape \
 		  test_extensions \
 		  test_ginpostinglist \
+		  test_int128 \
 		  test_integerset \
 		  test_json_parser \
 		  test_lfind \

src/test/modules/meson.build

@@ -24,6 +24,7 @@ subdir('test_dsm_registry')
 subdir('test_escape')
 subdir('test_extensions')
 subdir('test_ginpostinglist')
+subdir('test_int128')
 subdir('test_integerset')
 subdir('test_json_parser')
 subdir('test_lfind')

src/test/modules/test_int128/.gitignore

@@ -0,0 +1,2 @@
+/tmp_check/
+/test_int128

src/test/modules/test_int128/Makefile

@@ -0,0 +1,23 @@
+# src/test/modules/test_int128/Makefile
+
+PGFILEDESC = "test_int128 - test 128-bit integer arithmetic"
+
+PROGRAM = test_int128
+OBJS = $(WIN32RES) test_int128.o
+
+PG_CPPFLAGS = -I$(libpq_srcdir)
+PG_LIBS_INTERNAL += $(libpq_pgport)
+
+NO_INSTALL = 1
+TAP_TESTS = 1
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = src/test/modules/test_int128
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif

src/test/modules/test_int128/meson.build

@@ -0,0 +1,33 @@
+# Copyright (c) 2025, PostgreSQL Global Development Group
+
+test_int128_sources = files(
+  'test_int128.c',
+)
+
+if host_system == 'windows'
+  test_int128_sources += rc_bin_gen.process(win32ver_rc, extra_args: [
+    '--NAME', 'test_int128',
+    '--FILEDESC', 'test int128 program',])
+endif
+
+test_int128 = executable('test_int128',
+  test_int128_sources,
+  dependencies: [frontend_code, libpq],
+  kwargs: default_bin_args + {
+    'install': false,
+  },
+)
+testprep_targets += test_int128
+
+
+tests += {
+  'name': 'test_int128',
+  'sd': meson.current_source_dir(),
+  'bd': meson.current_build_dir(),
+  'tap': {
+    'tests': [
+      't/001_test_int128.pl',
+    ],
+    'deps': [test_int128],
+  },
+}

src/test/modules/test_int128/t/001_test_int128.pl

@@ -0,0 +1,27 @@
+# Copyright (c) 2025, PostgreSQL Global Development Group
+
+# Test 128-bit integer arithmetic code in int128.h
+
+use strict;
+use warnings FATAL => 'all';
+
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+# Run the test program with 1M iterations
+my $exe = "test_int128";
+my $size = 1_000_000;
+
+note "testing executable $exe";
+
+my ($stdout, $stderr) = run_command([ $exe, $size ]);
+
+SKIP:
+{
+	skip "no native int128 type", 2 if $stdout =~ /skipping tests/;
+
+	is($stdout, "", "test_int128: no stdout");
+	is($stderr, "", "test_int128: no stderr");
+}
+
+done_testing();

src/test/modules/test_int128/test_int128.c

@@ -0,0 +1,190 @@
+/*-------------------------------------------------------------------------
+ *
+ * test_int128.c
+ *	  Testbed for roll-our-own 128-bit integer arithmetic.
+ *
+ * This is a standalone test program that compares the behavior of an
+ * implementation in int128.h to an (assumed correct) int128 native type.
+ *
+ * Copyright (c) 2017-2025, PostgreSQL Global Development Group
+ *
+ *
+ * IDENTIFICATION
+ *	  src/test/modules/test_int128/test_int128.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres_fe.h"
+
+#include <time.h>
+
+/* Require a native int128 type */
+#ifdef HAVE_INT128
+
+/*
+ * By default, we test the non-native implementation in int128.h; but
+ * by predefining USE_NATIVE_INT128 to 1, you can test the native
+ * implementation, just to be sure.
+ */
+#ifndef USE_NATIVE_INT128
+#define USE_NATIVE_INT128 0
+#endif
+
+#include "common/int128.h"
+#include "common/pg_prng.h"
+
+/*
+ * We assume the parts of this union are laid out compatibly.
+ */
+typedef union
+{
+	int128		i128;
+	INT128		I128;
+	struct
+	{
+#ifdef WORDS_BIGENDIAN
+		int64		hi;
+		uint64		lo;
+#else
+		uint64		lo;
+		int64		hi;
+#endif
+	}			hl;
+}			test128;
+
+#define INT128_HEX_FORMAT	"%016" PRIx64 "%016" PRIx64
+
+/*
+ * Control version of comparator.
+ */
+static inline int
+my_int128_compare(int128 x, int128 y)
+{
+	if (x < y)
+		return -1;
+	if (x > y)
+		return 1;
+	return 0;
+}
+
+/*
+ * Main program.
+ *
+ * Generates a lot of random numbers and tests the implementation for each.
+ * The results should be reproducible, since we use a fixed PRNG seed.
+ *
+ * You can give a loop count if you don't like the default 1B iterations.
+ */
+int
+main(int argc, char **argv)
+{
+	long		count;
+
+	pg_prng_seed(&pg_global_prng_state, (uint64) time(NULL));
+
+	if (argc >= 2)
+		count = strtol(argv[1], NULL, 0);
+	else
+		count = 1000000000;
+
+	while (count-- > 0)
+	{
+		int64		x = pg_prng_uint64(&pg_global_prng_state);
+		int64		y = pg_prng_uint64(&pg_global_prng_state);
+		int64		z = pg_prng_uint64(&pg_global_prng_state);
+		test128		t1;
+		test128		t2;
+
+		/* check unsigned addition */
+		t1.hl.hi = x;
+		t1.hl.lo = y;
+		t2 = t1;
+		t1.i128 += (int128) (uint64) z;
+		int128_add_uint64(&t2.I128, (uint64) z);
+
+		if (t1.hl.hi != t2.hl.hi || t1.hl.lo != t2.hl.lo)
+		{
+			printf(INT128_HEX_FORMAT " + unsigned " PRIx64 "\n", x, y, z);
+			printf("native = " INT128_HEX_FORMAT "\n", t1.hl.hi, t1.hl.lo);
+			printf("result = " INT128_HEX_FORMAT "\n", t2.hl.hi, t2.hl.lo);
+			return 1;
+		}
+
+		/* check signed addition */
+		t1.hl.hi = x;
+		t1.hl.lo = y;
+		t2 = t1;
+		t1.i128 += (int128) z;
+		int128_add_int64(&t2.I128, z);
+
+		if (t1.hl.hi != t2.hl.hi || t1.hl.lo != t2.hl.lo)
+		{
+			printf(INT128_HEX_FORMAT " + signed " PRIx64 "\n", x, y, z);
+			printf("native = " INT128_HEX_FORMAT "\n", t1.hl.hi, t1.hl.lo);
+			printf("result = " INT128_HEX_FORMAT "\n", t2.hl.hi, t2.hl.lo);
+			return 1;
+		}
+
+		/* check multiplication */
+		t1.i128 = (int128) x * (int128) y;
+
+		t2.hl.hi = t2.hl.lo = 0;
+		int128_add_int64_mul_int64(&t2.I128, x, y);
+
+		if (t1.hl.hi != t2.hl.hi || t1.hl.lo != t2.hl.lo)
+		{
+			printf(PRIx64 " * " PRIx64 "\n", x, y);
+			printf("native = " INT128_HEX_FORMAT "\n", t1.hl.hi, t1.hl.lo);
+			printf("result = " INT128_HEX_FORMAT "\n", t2.hl.hi, t2.hl.lo);
+			return 1;
+		}
+
+		/* check comparison */
+		t1.hl.hi = x;
+		t1.hl.lo = y;
+		t2.hl.hi = z;
+		t2.hl.lo = pg_prng_uint64(&pg_global_prng_state);
+
+		if (my_int128_compare(t1.i128, t2.i128) !=
+			int128_compare(t1.I128, t2.I128))
+		{
+			printf("comparison failure: %d vs %d\n",
+				   my_int128_compare(t1.i128, t2.i128),
+				   int128_compare(t1.I128, t2.I128));
+			printf("arg1 = " INT128_HEX_FORMAT "\n", t1.hl.hi, t1.hl.lo);
+			printf("arg2 = " INT128_HEX_FORMAT "\n", t2.hl.hi, t2.hl.lo);
+			return 1;
+		}
+
+		/* check case with identical hi parts; above will hardly ever hit it */
+		t2.hl.hi = x;
+
+		if (my_int128_compare(t1.i128, t2.i128) !=
+			int128_compare(t1.I128, t2.I128))
+		{
+			printf("comparison failure: %d vs %d\n",
+				   my_int128_compare(t1.i128, t2.i128),
+				   int128_compare(t1.I128, t2.I128));
+			printf("arg1 = " INT128_HEX_FORMAT "\n", t1.hl.hi, t1.hl.lo);
+			printf("arg2 = " INT128_HEX_FORMAT "\n", t2.hl.hi, t2.hl.lo);
+			return 1;
+		}
+	}
+
+	return 0;
+}
+
+#else							/* ! HAVE_INT128 */
+
+/*
+ * For now, do nothing if we don't have a native int128 type.
+ */
+int
+main(int argc, char **argv)
+{
+	printf("skipping tests: no native int128 type\n");
+	return 0;
+}
+
+#endif