spawn: Allow passing file descriptors to the child process

Add vte_pty_spawn_with_fds_async() and vte_terminal_spawn_with_fds_async()
that take an array of file descriptors, and an array of integers specifying
where to assign the file descriptors to in the child process.

This also fixes the equivalent of gspawn/gsubprocess bug
https://gitlab.gnome.org/GNOME/glib/-/issues/2097 when using
these new functions (e.g. in gnome-terminal).

1 files changed, 46 insertions, 2 deletions

diff --git a/src/spawn.hh b/src/spawn.hh
index c6a5b1f3..26b0ec0b 100644
--- a/src/spawn.hh
+++ b/src/spawn.hh
@@ -18,6 +18,7 @@
 #pragma once
 
 #include <memory>
+#include <vector>
 
 #include <glib.h>
 #include <gio/gio.h>
@@ -47,6 +48,13 @@ private:
         vte::glib::StrvPtr m_argv;
         vte::glib::StrvPtr m_envv;
 
+        std::vector<vte::libc::FD> m_fds{};
+
+        // these 3 are placeholder elements for the PTY peer fd being mapped to 0, 1, 2 later
+        // we preallocate this here so that the child setup function doesn't do any
+        // allocations
+        std::vector<std::pair<int,int>> m_fd_map{{-1, 0}, {-1, 1}, {-1, 2}};
+
         child_setup_type m_child_setup{(void(*)(void*))0};
         void* m_child_setup_data{nullptr};
         GDestroyNotify m_child_setup_data_destroy{nullptr};
@@ -119,6 +127,30 @@ public:
                 m_child_setup_data_destroy = destroy;
         }
 
+        void add_fds(int const* fds,
+                     int n_fds)
+        {
+                m_fds.reserve(m_fds.size() + n_fds);
+                for (auto i = int{0}; i < n_fds; ++i)
+                        m_fds.emplace_back(fds[i]);
+        }
+
+        void add_map_fds(int const* fds,
+                         int n_fds,
+                         int const* map_fds,
+                         int n_map_fds)
+        {
+                m_fd_map.reserve(m_fd_map.size() + n_fds);
+                for (auto i = int{0}; i < n_fds; ++i)
+                        m_fd_map.emplace_back(fds[i], i < n_map_fds ? map_fds[i] : -1);
+        }
+
+        void add_map_fd(int fd,
+                        int map_to)
+        {
+                add_map_fds(&fd, 1, &map_to, 1);
+        }
+
         void set_no_inherit_environ()    noexcept { m_inherit_environ = false;      }
         void set_no_systemd_scope()      noexcept { m_systemd_scope = false;        }
         void set_require_systemd_scope() noexcept { m_require_systemd_scope = true; }
@@ -142,7 +174,19 @@ public:
 
         void prepare_environ();
 
-        int exec() const noexcept;
+        enum class ExecError {
+                CHDIR,
+                DUP,
+                DUP2,
+                EXEC,
+                GETPTPEER,
+                SCTTY,
+                SETSID,
+                SIGMASK,
+                UNSET_CLOEXEC,
+        };
+
+        ExecError exec(vte::libc::FD& child_report_error_pipe_write) noexcept;
 
 }; // class SpawnContext
 
@@ -161,7 +205,7 @@ private:
         pid_t m_pid{-1};
         bool m_kill_pid{true};
 
-        auto& context() const noexcept { return m_context; }
+        auto& context() noexcept { return m_context; }
 
         bool prepare(vte::glib::Error& error);
         bool run(vte::glib::Error& error) noexcept;