Switch to using std::filesystem

Originally, the minimum required GCC version was version 6, which didn't
have support for the C++17 Filesystem library. However, with our minimum
requirement being GCC version 9, we now can use std::filesystem and drop
a few of our hand-rolled implementations.

Ideally, I'd even go so far as to even cut down blackhole.cc, which uses
access() to check whether the temporary directory is writable and uses
the best possible but writable one. Obviously, this isn't portable, but
given that ip2unix for example will probably never work natively on
Windows, I think it's fine to leave it as is, since using
std::filesystem APIs won't actually assure that the underlying syscall
would be access() anymore.

Nevertheless however, this should pave the way to port ip2unix to
Darwin and possibly BSD one day.

Signed-off-by: aszlig <[email protected]>

Author: aszlig

src/blackhole.cc

@@ -6,14 +6,15 @@
 #include <climits>
 #include <cstdlib>
 #include <cstring>
+#include <filesystem>
 #include <initializer_list>
 #include <string>
 
 #include <errno.h>
 #include <sys/stat.h>
 #include <unistd.h>
 
-static bool is_writable_dir(const std::string &dir)
+static bool is_writable_dir(const std::filesystem::path &dir)
 {
     int old_errno = errno;
 
@@ -40,7 +41,7 @@ static bool is_writable_dir(const std::string &dir)
     return S_ISDIR(st.st_mode);
 }
 
-static std::string get_tmpdir(void)
+static std::filesystem::path get_tmpdir(void)
 {
     for (const char *tryenv : {"TMPDIR", "TMP", "TEMP", "TEMPDIR"}) {
         const char *tmpdir = getenv(tryenv);
@@ -62,15 +63,10 @@ static std::string get_tmpdir(void)
     if (is_writable_dir("/var/tmp"))
         return "/var/tmp";
 
-    int old_errno = errno;
-    char *workdir = get_current_dir_name();
-    errno = old_errno;
-    if (workdir != nullptr) {
-        std::string wdir_str(workdir);
-        free(workdir);
-        if (is_writable_dir(wdir_str))
-            return wdir_str;
-    }
+    std::string workdir = std::filesystem::current_path();
+
+    if (is_writable_dir(workdir))
+        return workdir;
 
     LOG(FATAL) << "Unable to get temporary directory.";
     std::abort();
@@ -91,9 +87,9 @@ BlackHole::BlackHole()
     : tmpdir(std::nullopt)
     , filepath(std::nullopt)
 {
-    static std::string tempdir = get_tmpdir();
+    static std::filesystem::path tempdir = get_tmpdir();
 
-    std::string bh_template = tempdir + "/ip2unix.XXXXXX";
+    std::string bh_template = tempdir / "ip2unix.XXXXXX";
 
     char *c_bh_template = strdup(bh_template.c_str());
 

src/rules/parse.cc

@@ -5,6 +5,7 @@
 
 #include <algorithm>
 #include <cstddef>
+#include <filesystem>
 #include <iostream>
 #include <optional>
 #include <string>
@@ -323,14 +324,6 @@ static void print_arg_error(size_t rulepos, const std::string &arg, size_t pos,
                   << ' ' << msg << std::endl;
 }
 
-std::string make_absolute(const std::string &path)
-{
-    if (path.empty() || path[0] == '/')
-        return path;
-
-    return std::string(get_current_dir_name()) + '/' + path;
-}
-
 std::optional<Rule> parse_rule_arg(size_t rulepos, const std::string &arg)
 {
     std::string buf;
@@ -346,7 +339,7 @@ std::optional<Rule> parse_rule_arg(size_t rulepos, const std::string &arg)
             if (i == arglen || arg[i] == ',') {
                 /* Handle key=value options. */
                 if (key.value() == "path") {
-                    rule.socket_path = make_absolute(buf);
+                    rule.socket_path = std::filesystem::absolute(buf);
 #ifdef SYSTEMD_SUPPORT
                 } else if (key.value() == "systemd") {
                     rule.socket_activation = true;