basic: Override glibc's sys/param.h header with an empty file

Instead of unconditionally including sys/param.h in
macro-fundamental.h which itself includes a bunch of other unnecessary
headers, let's override it with an empty file to avoid it from overriding
our MAX() macro. We can't make including it an error as it's included (
for seemingly no good reason) by <resolv.h>.

src/basic/include/sys/param.h

@@ -0,0 +1,8 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+/* sys/param.h from glibc unconditionally overrides the MIN() and MAX() macros which interferes with our own
+ * MAX() macro. It also includes a bunch of other headers transitively so we don't want to include
+ * sys/param.h in macro-fundamental.h unconditionally. We'd like to make including this file an error but
+ * unfortunately <resolv.h> includes it. However, <resolv.h> doesn't actually make use of anything from
+ * sys/param.h, so we override it with an empty file so it can't mess with our macros. */

src/basic/macro.h

@@ -5,7 +5,6 @@
 #include <errno.h>
 #include <inttypes.h>
 #include <stdbool.h>
-#include <sys/param.h>
 #include <sys/sysmacros.h>
 #include <sys/types.h>
 

src/basic/pidref.h

@@ -1,6 +1,8 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 #pragma once
 
+#include <signal.h>
+
 #include "macro.h"
 #include "memory-util.h"
 

src/core/ipe-setup.c

@@ -1,5 +1,7 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 
+#include <unistd.h>
+
 #include "alloc-util.h"
 #include "conf-files.h"
 #include "copy.h"

src/fundamental/macro-fundamental.h

@@ -7,13 +7,6 @@
 #include <stddef.h>
 #include <stdint.h>
 
-/* This header unconditionally defines MAX() so include it here already so
- * it won't override our own definition of MAX() that we define later in this
- * file. */
-#if !SD_BOOT
-#include <sys/param.h>
-#endif
-
 /* Temporarily disable some warnings */
 #define DISABLE_WARNING_DEPRECATED_DECLARATIONS                         \
         _Pragma("GCC diagnostic push");                                 \

src/libsystemd/sd-journal/lookup3.c

@@ -47,13 +47,10 @@ on 1 byte), but shoehorning those bytes into integers efficiently is messy.
 */
 /* #define SELF_TEST 1 */
 
+#include <endian.h>    /* attempt to define endianness */
 #include <stdint.h>     /* defines uint32_t etc */
 #include <stdio.h>      /* defines printf for tests */
-#include <sys/param.h>  /* attempt to define endianness */
 #include <time.h>       /* defines time_t for timings in the test */
-#ifdef linux
-# include <endian.h>    /* attempt to define endianness */
-#endif
 
 _Pragma("GCC diagnostic ignored \"-Wimplicit-fallthrough\"")
 

src/network/test-network.c

@@ -1,7 +1,6 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 
 #include <arpa/inet.h>
-#include <sys/param.h>
 
 #include "sd-device.h"
 

src/shared/initreq.h

@@ -6,7 +6,7 @@
 
 #pragma once
 
-#include <sys/param.h>
+#include <limits.h>
 
 #if defined(__FreeBSD_kernel__)
 #  define INIT_FIFO  "/etc/.initctl"
@@ -25,13 +25,6 @@
 #define INIT_CMD_UNSETENV	7
 
 #define INIT_CMD_CHANGECONS	12345
-
-#ifdef MAXHOSTNAMELEN
-#  define INITRQ_HLEN	MAXHOSTNAMELEN
-#else
-#  define INITRQ_HLEN	64
-#endif
-
 /*
  *	This is what BSD 4.4 uses when talking to init.
  *	Linux doesn't use this right now.
@@ -39,7 +32,7 @@
 struct init_request_bsd {
         char	gen_id[8];		/* Beats me.. telnetd uses "fe" */
         char	tty_id[16];		/* Tty name minus /dev/tty      */
-        char	host[INITRQ_HLEN];	/* Hostname                     */
+        char	host[HOST_NAME_MAX];	/* Hostname                     */
         char	term_type[16];		/* Terminal type                */
         int	signal;			/* Signal to send               */
         int	pid;			/* Process to send to           */