Unify handling of BSD systems where applicable

src/common.cpp

@@ -34,7 +34,7 @@
 #include <sys/utsname.h>
 #endif
 
-#ifdef __FreeBSD__
+#ifdef __BSD__
 #include <sys/sysctl.h>
 #elif defined(__APPLE__)
 #include <mach-o/dyld.h>
@@ -1994,10 +1994,10 @@ std::string get_executable_path(const char *argv0) {
     // https://opensource.apple.com/source/adv_cmds/adv_cmds-163/ps/print.c
     uint32_t buffSize = sizeof buff;
     if (_NSGetExecutablePath(buff, &buffSize) == 0) return std::string(buff);
-#elif defined(__FreeBSD__)
-    // FreeBSD does not have /proc by default, but it can be mounted as procfs via the
-    // Linux compatibility layer. Per sysctl(3), passing in a process ID of -1 returns
-    // the value for the current process.
+#elif defined(__BSD__)
+    // BSDs do not have /proc by default, (although it can be mounted as procfs via the Linux
+    // compatibility layer). We can use sysctl instead: per sysctl(3), passing in a process ID of -1
+    // returns the value for the current process.
     size_t buff_size = sizeof buff;
     int name[] = {CTL_KERN, KERN_PROC, KERN_PROC_PATHNAME, -1};
     int result = sysctl(name, sizeof(name) / sizeof(int), buff, &buff_size, nullptr, 0);

src/common.h

@@ -22,6 +22,11 @@
 #include "fallback.h"  // IWYU pragma: keep
 #include "maybe.h"
 
+// Create a generic define for all BSD platforms
+#if defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__) || defined(__DragonFly__)
+#define __BSD__
+#endif
+
 // PATH_MAX may not exist.
 #ifndef PATH_MAX
 #define PATH_MAX 4096