Introduce sc_arg_max() helper

Just a cast and an assert.

src/basic/env-util.c

@@ -72,7 +72,7 @@ bool env_value_is_valid(const char *e) {
          * either. Discounting the shortest possible variable name of
          * length 1, the equal sign and trailing NUL this hence leaves
          * ARG_MAX-3 as longest possible variable value. */
-        if (strlen(e) > (size_t) sysconf(_SC_ARG_MAX) - 3)
+        if (strlen(e) > sc_arg_max() - 3)
                 return false;
 
         return true;
@@ -95,7 +95,7 @@ bool env_assignment_is_valid(const char *e) {
          * be > ARG_MAX, hence the individual variable assignments
          * cannot be either, but let's leave room for one trailing NUL
          * byte. */
-        if (strlen(e) > (size_t) sysconf(_SC_ARG_MAX) - 1)
+        if (strlen(e) > sc_arg_max() - 1)
                 return false;
 
         return true;

src/basic/env-util.h

@@ -4,10 +4,17 @@
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdio.h>
+#include <unistd.h>
 
 #include "macro.h"
 #include "string.h"
 
+static inline size_t sc_arg_max(void) {
+        long l = sysconf(_SC_ARG_MAX);
+        assert(l > 0);
+        return (size_t) l;
+}
+
 bool env_name_is_valid(const char *e);
 bool env_value_is_valid(const char *e);
 bool env_assignment_is_valid(const char *e);

src/basic/process-util.c

@@ -25,6 +25,7 @@
 #include "alloc-util.h"
 #include "architecture.h"
 #include "escape.h"
+#include "env-util.h"
 #include "fd-util.h"
 #include "fileio.h"
 #include "fs-util.h"
@@ -126,12 +127,9 @@ int get_process_cmdline(pid_t pid, size_t max_length, bool comm_fallback, char *
         if (r < 0)
                 return r;
 
-        if (max_length == 0) {
+        if (max_length == 0)
                 /* This is supposed to be a safety guard against runaway command lines. */
-                long l = sysconf(_SC_ARG_MAX);
-                assert(l > 0);
-                max_length = l;
-        }
+                max_length = sc_arg_max();
 
         if (max_length == 1) {
 

src/journal/journald-context.c

@@ -7,6 +7,7 @@
 #include "alloc-util.h"
 #include "audit-util.h"
 #include "cgroup-util.h"
+#include "env-util.h"
 #include "fd-util.h"
 #include "fileio.h"
 #include "fs-util.h"
@@ -76,18 +77,14 @@ static size_t cache_max(void) {
                 if (r < 0) {
                         log_warning_errno(r, "Cannot query /proc/meminfo for MemTotal: %m");
                         cached = CACHE_MAX_FALLBACK;
-                } else {
+                } else
                         /* Cache entries are usually a few kB, but the process cmdline is controlled by the
                          * user and can be up to _SC_ARG_MAX, usually 2MB. Let's say that approximately up to
                          * 1/8th of memory may be used by the cache.
                          *
                          * In the common case, this formula gives 64 cache entries for each GB of RAM.
                          */
-                        long l = sysconf(_SC_ARG_MAX);
-                        assert(l > 0);
-
-                        cached = CLAMP(mem_total / 8 / (uint64_t) l, CACHE_MAX_MIN, CACHE_MAX_MAX);
-                }
+                        cached = CLAMP(mem_total / 8 / sc_arg_max(), CACHE_MAX_MIN, CACHE_MAX_MAX);
         }
 
         return cached;