fix(process): report Linux exec failures

src/platform_linux.cpp

@@ -6,6 +6,7 @@
 #include <izo/system.hpp>
 
 #include <dlfcn.h>
+#include <fcntl.h>
 #include <signal.h>
 #include <sys/sysinfo.h>
 #include <sys/utsname.h>
@@ -75,19 +76,42 @@ std::filesystem::path get_known_path(known_path path, std::string* error_message
 
 process_result launch_process(const process_options& options) {
     if (options.executable.empty()) return {false, 0, "Executable path is required"};
+    int error_pipe[2];
+    if (pipe2(error_pipe, O_CLOEXEC) != 0) return {false, 0, std::strerror(errno)};
     const pid_t child = fork();
-    if (child < 0) return {false, 0, std::strerror(errno)};
+    if (child < 0) {
+        const std::string error = std::strerror(errno);
+        close(error_pipe[0]);
+        close(error_pipe[1]);
+        return {false, 0, error};
+    }
     if (child == 0) {
+        close(error_pipe[0]);
         if (options.detached) setsid();
-        if (!options.working_directory.empty() && chdir(options.working_directory.c_str()) != 0) _exit(126);
+        if (!options.working_directory.empty() && chdir(options.working_directory.c_str()) != 0) {
+            const int error = errno;
+            write(error_pipe[1], &error, sizeof(error));
+            _exit(126);
+        }
         std::vector<std::string> values{options.executable.string()};
         values.insert(values.end(), options.arguments.begin(), options.arguments.end());
         std::vector<char*> argv;
         for (auto& value : values) argv.push_back(value.data());
         argv.push_back(nullptr);
         execvp(argv[0], argv.data());
+        const int error = errno;
+        write(error_pipe[1], &error, sizeof(error));
         _exit(127);
     }
+    close(error_pipe[1]);
+    int child_error = 0;
+    const ssize_t error_bytes = read(error_pipe[0], &child_error, sizeof(child_error));
+    close(error_pipe[0]);
+    if (error_bytes > 0) {
+        int status = 0;
+        while (waitpid(child, &status, 0) < 0 && errno == EINTR) {}
+        return {false, 0, std::strerror(child_error)};
+    }
     std::thread([child] {
         int status = 0;
         while (waitpid(child, &status, 0) < 0 && errno == EINTR) {}