test-sizeof: add a helper which prints variable sizes and signedness

This helps to understand misleading gcc warnings about type mismatches.

.gitignore

@@ -248,6 +248,7 @@
 /test-sched-prio
 /test-selinux
 /test-set
+/test-sizeof
 /test-sigbus
 /test-signal-util
 /test-siphash24

Makefile.am

@@ -1480,7 +1480,8 @@ tests += \
 	test-install-root \
 	test-rlimit-util \
 	test-signal-util \
-	test-selinux
+	test-selinux \
+	test-sizeof
 
 if HAVE_ACL
 tests += \
@@ -1880,6 +1881,12 @@ test_selinux_SOURCES = \
 test_selinux_LDADD = \
 	libshared.la
 
+test_sizeof_SOURCES = \
+	src/test/test-sizeof.c
+
+test_sizeof_LDADD = \
+	libshared.la
+
 BUILT_SOURCES += \
 	src/test/test-hashmap-ordered.c
 

src/test/test-sizeof.c

@@ -0,0 +1,53 @@
+/***
+  This file is part of systemd.
+
+  Copyright 2016 Zbigniew Jędrzejewski-Szmek
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include "log.h"
+#include "time-util.h"
+
+/* Print information about various types. Useful when diagnosing
+ * gcc diagnostics on an unfamiliar architecture. */
+
+#pragma GCC diagnostic ignored "-Wtype-limits"
+
+#define info(t)                                                 \
+        log_info("%s → %zu bits%s", STRINGIFY(t),               \
+                 sizeof(t)*CHAR_BIT,                            \
+                 strstr(STRINGIFY(t), "signed") ? "" :          \
+                 ((t)-1 < (t)0 ? ", signed" : ", unsigned"));
+
+int main(void) {
+        info(char);
+        info(signed char);
+        info(unsigned char);
+        info(short unsigned);
+        info(unsigned);
+        info(long unsigned);
+        info(long long unsigned);
+
+        info(float);
+        info(double);
+        info(long double);
+
+        info(size_t);
+        info(ssize_t);
+        info(time_t);
+        info(usec_t);
+
+        return 0;
+}