Change to execution paths to binary paths (#200)

Previously, it used argv[0] for the execution path, which is fine in
most cases, but in my case, it is not.
The thing is, I use NixOS, and I have created a Nix module for BeamMP.
When running BeamMP-Launcher, it tries to check for updates, and fails
because of the SHA hash.
There are other ways around this, such as setting the execution
directory, but I think this is a far clearer approach

---

By creating this pull request, I understand that code that is AI
generated or otherwise automatically generated may be rejected without
further discussion.
I declare that I fully understand all code I pushed into this PR, and
wrote all this code myself and own the rights to this code.

include/Startup.h

@@ -13,6 +13,7 @@
 
 void InitLauncher();
 beammp_fs_string GetEP(const beammp_fs_char* P = nullptr);
+std::filesystem::path GetBP(const beammp_fs_char* P = nullptr);
 std::filesystem::path GetGamePath();
 std::string GetVer();
 std::string GetPatch();

include/Utils.h

@@ -236,7 +236,7 @@ namespace Utils {
             for (size_t i = 0; i < sha256_len; i++) {
                 char buf[3];
                 sprintf(buf, "%02x", sha256_value[i]);
-                buf[2] = NULL;
+                buf[2] = '\0';
                 result += buf;
             }
             return result;
@@ -280,7 +280,7 @@ namespace Utils {
             for (size_t i = 0; i < sha256_len; i++) {
                 char buf[3];
                 sprintf(buf, "%02x", sha256_value[i]);
-                buf[2] = NULL;
+                buf[2] = '\0';
                 result += buf;
             }
             return result;

src/Startup.cpp

@@ -14,7 +14,10 @@
 #if defined(_WIN32)
 #elif defined(__linux__)
 #include <unistd.h>
-#endif
+#elif defined (__APPLE__)
+#include <unistd.h>
+#include <libproc.h>
+#endif // __APPLE__
 #include "Http.h"
 #include "Logger.h"
 #include "Network/network.hpp"
@@ -94,6 +97,34 @@ beammp_fs_string GetEP(const beammp_fs_char* P) {
     }();
     return Ret;
 }
+
+fs::path GetBP(const beammp_fs_char* P) {
+    fs::path fspath = {};
+#if defined(_WIN32)
+    beammp_fs_char path[256];
+    GetModuleFileNameW(nullptr, path, sizeof(path));
+    fspath = path;
+#elif defined(__linux__)
+    fspath = fs::canonical("/proc/self/exe");
+#elif defined(__APPLE__)
+    pid_t pid = getpid();
+    char path[PROC_PIDPATHINFO_MAXSIZE];
+    // While this is fine for a raw executable,
+    // an application bundle is read-only and these files
+    // should instead be placed in Application Support.
+    proc_pidpath(pid, path, sizeof(path));
+    fspath = std::string(path);
+ #else
+    fspath = beammp_fs_string(P);
+#endif
+    fspath = fs::weakly_canonical(fspath.string() + "/..");
+#if defined(_WIN32)
+    return fspath.wstring();
+#else
+    return fspath.string();
+#endif
+}
+
 #if defined(_WIN32)
 void ReLaunch() {
     std::wstring Arg;
@@ -103,7 +134,7 @@ void ReLaunch() {
     }
     info("Relaunch!");
     system("cls");
-    ShellExecuteW(nullptr, L"runas", (GetEP() + GetEN()).c_str(), Arg.c_str(), nullptr, SW_SHOWNORMAL);
+    ShellExecuteW(nullptr, L"runas", (GetBP() / GetEN()).c_str(), Arg.c_str(), nullptr, SW_SHOWNORMAL);
     ShowWindow(GetConsoleWindow(), 0);
     std::this_thread::sleep_for(std::chrono::seconds(1));
     exit(1);
@@ -114,7 +145,7 @@ void URelaunch() {
         Arg += Utils::ToWString(options.argv[c - 1]);
         Arg += L" ";
     }
-    ShellExecuteW(nullptr, L"open", (GetEP() + GetEN()).c_str(), Arg.c_str(), nullptr, SW_SHOWNORMAL);
+    ShellExecuteW(nullptr, L"open", (GetBP() / GetEN()).c_str(), Arg.c_str(), nullptr, SW_SHOWNORMAL);
     ShowWindow(GetConsoleWindow(), 0);
     std::this_thread::sleep_for(std::chrono::seconds(1));
     exit(1);
@@ -128,7 +159,7 @@ void ReLaunch() {
     }
     info("Relaunch!");
     system("clear");
-    int ret = execv(options.executable_name.c_str(), const_cast<char**>(options.argv));
+    int ret = execv((GetBP() / GetEN()).c_str(), const_cast<char**>(options.argv));
     if (ret < 0) {
         error(std::string("execv() failed with: ") + strerror(errno) + ". Failed to relaunch");
         exit(1);
@@ -137,7 +168,7 @@ void ReLaunch() {
     exit(1);
 }
 void URelaunch() {
-    int ret = execv(options.executable_name.c_str(), const_cast<char**>(options.argv));
+    int ret = execv((GetBP() / GetEN()).c_str(), const_cast<char**>(options.argv));
     if (ret < 0) {
         error(std::string("execv() failed with: ") + strerror(errno) + ". Failed to relaunch");
         exit(1);
@@ -169,9 +200,9 @@ void CheckForUpdates(const std::string& CV) {
         "https://backend.beammp.com/version/launcher?branch=" + Branch + "&pk=" + PublicKey);
 
     transform(LatestHash.begin(), LatestHash.end(), LatestHash.begin(), ::tolower);
-    beammp_fs_string EP(GetEP() + GetEN()), Back(GetEP() + beammp_wide("BeamMP-Launcher.back"));
+    beammp_fs_string BP(GetBP() / GetEN()), Back(GetBP() / beammp_wide("BeamMP-Launcher.back"));
 
-    std::string FileHash = Utils::GetSha256HashReallyFastFile(EP);
+    std::string FileHash = Utils::GetSha256HashReallyFastFile(BP);
 
     if (FileHash != LatestHash && IsOutdated(Version(VersionStrToInts(GetVer() + GetPatch())), Version(VersionStrToInts(LatestVersion)))) {
         if (!options.no_update) {
@@ -184,16 +215,16 @@ void CheckForUpdates(const std::string& CV) {
                 "https://backend.beammp.com/builds/launcher?download=true"
                 "&pk="
                     + PublicKey + "&branch=" + Branch,
-                beammp_wide("new_") + EP, LatestHash);
+                beammp_wide("new_") + BP, LatestHash);
             std::error_code ec;
             fs::remove(Back, ec);
             if (ec == std::errc::permission_denied) {
                 error("Failed to remove old backup file: " + ec.message() + ". Using alternative name.");
-                fs::rename(EP, Back + beammp_wide(".") + Utils::ToWString(FileHash.substr(0, 8)));
+                fs::rename(BP, Back + beammp_wide(".") + Utils::ToWString(FileHash.substr(0, 8)));
             } else {
-                fs::rename(EP, Back);
+                fs::rename(BP, Back);
             }
-            fs::rename(beammp_wide("new_") + EP, EP);
+            fs::rename(beammp_wide("new_") + BP, BP);
             URelaunch();
 #endif
         } else {
@@ -254,8 +285,8 @@ void InitLauncher() {
 }
 #endif
 
-size_t DirCount(const std::filesystem::path& path) {
+size_t DirCount(const fs::path& path) {
-    return (size_t)std::distance(std::filesystem::directory_iterator { path }, std::filesystem::directory_iterator {});
+    return (size_t)std::distance(fs::directory_iterator { path }, fs::directory_iterator {});
 }
 
 void CheckMP(const beammp_fs_string& Path) {