util-lib: save/restore errno in cleanup calls

We should be careful with errno in cleanup functions, and not alter it
under any circumstances. In the safe_close cleanup handlers we are
already safe in that regard, but let's add similar protections on other
cleanup handlers that invoke system calls.

Why bother? Cleanup handlers insert code at function return in
non-obvious ways. Hence, code that sets errno and returns should not be
confused by us overrding the errno from a cleanup handler.

This is a paranoia fix only, I am not aware where this actually mattered
in real-life situations.

src/basic/fs-util.h

@@ -29,6 +29,7 @@
 #include <unistd.h>
 
 #include "time-util.h"
+#include "util.h"
 
 int unlink_noerrno(const char *path);
 
@@ -89,13 +90,14 @@ int chase_symlinks(const char *path_with_prefix, const char *root, unsigned flag
 
 /* Useful for usage with _cleanup_(), removes a directory and frees the pointer */
 static inline void rmdir_and_free(char *p) {
+        PROTECT_ERRNO;
         (void) rmdir(p);
         free(p);
 }
 DEFINE_TRIVIAL_CLEANUP_FUNC(char*, rmdir_and_free);
 
 static inline void unlink_and_free(char *p) {
-        (void) unlink(p);
+        (void) unlink_noerrno(p);
         free(p);
 }
 DEFINE_TRIVIAL_CLEANUP_FUNC(char*, unlink_and_free);

src/basic/process-util.c

@@ -796,6 +796,8 @@ void sigkill_wait(pid_t pid) {
 }
 
 void sigkill_waitp(pid_t *pid) {
+        PROTECT_ERRNO;
+
         if (!pid)
                 return;
         if (*pid <= 1)

src/basic/rm-rf.h

@@ -22,6 +22,8 @@
 
 #include <sys/stat.h>
 
+#include "util.h"
+
 typedef enum RemoveFlags {
         REMOVE_ONLY_DIRECTORIES = 1,
         REMOVE_ROOT = 2,
@@ -34,6 +36,7 @@ int rm_rf(const char *path, RemoveFlags flags);
 
 /* Useful for usage with _cleanup_(), destroys a directory and frees the pointer */
 static inline void rm_rf_physical_and_free(char *p) {
+        PROTECT_ERRNO;
         (void) rm_rf(p, REMOVE_ROOT|REMOVE_PHYSICAL);
         free(p);
 }