From e489a2db5a1e56e66f6df12642ad8cfd988d4b30 Mon Sep 17 00:00:00 2001
From: _ov4 <ov4@ov4.org>
Date: Wed, 16 Sep 2026 11:28:14 +0000
Subject: implement subshell, and fix vector operator[] unvalid index

---
 src/eval.cc | 88 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 82 insertions(+), 6 deletions(-)

(limited to 'src/eval.cc')

diff --git a/src/eval.cc b/src/eval.cc
index 0192ab7..6d16cf7 100644
--- a/src/eval.cc
+++ b/src/eval.cc
@@ -30,7 +30,7 @@ extern char **environ;
 namespace ov4
 {
 
-int eval_exe(string s, bool is_aync)
+int eval_exe(const string &s, bool is_aync)
 {
     loggerln("eval_exe: receive {}", s);
 
@@ -69,10 +69,13 @@ int eval_exe(string s, bool is_aync)
 
         sigprocmask(SIG_SETMASK, &prev, nullptr);
 
-        // program inside execve may use SIGTTIN/SIGTTOU so just restore in child
+        // program inside execve may use SIGTTIN/SIGTTOU
+        // so just restore in child
         sigprocmask(SIG_UNBLOCK, &block_io, nullptr);
         execve(cmd_c, argv, environ);
 
+        // execve: if success, never returns
+
         wrap_eliminator(cmdline);
         cout << cmdline << flush;
         switch (errno)
@@ -135,12 +138,85 @@ int eval_exe(string s, bool is_aync)
     return 0;
 }
 
-int eval_tree_cd(size_t i, const T_lexer &lexer_instance)
+int eval_subshell(size_t i, const T_lexer &lexer_instance)
+{
+    println("eval_tree_cd: processing subshell");
+
+    // TODO: implement async
+    bool is_aync = false;
+
+    char cmdline[] = "subshell";
+
+    // block_io signals can stop shell
+    // when child is at foreground, parent shell is at background
+    sigprocmask(SIG_BLOCK, &block_io, nullptr);
+
+    sigset_t prev;
+    block_all(&prev);
+
+    shell_pgid = getpgid(0);
+    pid_t pid = fork();
+    
+    if (pid == 0) // child
+    {
+        setpgid(0, 0);
+        if (!is_aync) // foreground
+            tcsetpgrp(tty_fd, getpgrp());
+
+        sigprocmask(SIG_SETMASK, &prev, nullptr);
+
+        // program inside execve may use SIGTTIN/SIGTTOU
+        // so just restore in child
+        sigprocmask(SIG_UNBLOCK, &block_io, nullptr);
+        eval_tree_cd(i, lexer_instance, true);
+        exit(0);
+    }
+
+    // parent
+
+    exit_required_pid = pid;
+
+    if (!is_aync)  // foreground
+    {   
+        addjob(pid, FG, cmdline); 
+        sigset_t prev_with_sigchld_blocked = prev;
+        sigaddset(&prev_with_sigchld_blocked, SIGCHLD);
+        sigprocmask(SIG_SETMASK, &prev_with_sigchld_blocked, NULL);
+        waitfg(pid);
+        sigprocmask(SIG_SETMASK, &prev, NULL);
+
+        return exit_code;
+    }
+    else // background
+    {
+        addjob(pid, BG, cmdline);
+        sigprocmask(SIG_SETMASK, &prev, NULL);
+        cout << "[" << pid2jid(pid) << "] (" << pid << ") " << cmdline;
+
+        // POSIX:
+        // async command returns 0 immediately
+        // TODO: recurring async 
+        return 0;
+    }
+}
+
+int eval_tree_cd(size_t i, const T_lexer &lexer_instance, bool inside_subshell)
 {
     // TODO: async
 
     int ret = -1;
 
+    println("eval_tree_cd: processing {} subshell {}", i, (lexer_instance.ast[i].subshell ? "TRUE" : "FALSE"));
+
+    // if it's a subshell, and current AST's subshell status is not subshell
+    // (subshell should be forkerd already, then set inside_subshell = true)
+    // fork itself
+    if (lexer_instance.ast[i].subshell && !inside_subshell)
+    {
+        eval_subshell(i, lexer_instance);
+        return 0;
+    }
+
     if (lexer_instance.ast[i].token_type == TEXT)
     {
         ret = eval_exe(lexer_instance.ast[i].command_text, false);
@@ -149,7 +225,7 @@ int eval_tree_cd(size_t i, const T_lexer &lexer_instance)
 
     if (lexer_instance.ast[i].left != string::npos)
     {
-        ret = eval_tree_cd(lexer_instance.ast[i].left, lexer_instance);
+        ret = eval_tree_cd(lexer_instance.ast[i].left, lexer_instance, false);
     }
 
     if (lexer_instance.ast[i].right != string::npos)
@@ -157,7 +233,7 @@ int eval_tree_cd(size_t i, const T_lexer &lexer_instance)
         if (lexer_instance.ast[i].token_type == LOGIC_AND && ret != 0) return ret;
         if (lexer_instance.ast[i].token_type == LOGIC_OR && ret == 0) return ret;
         
-        ret = eval_tree_cd(lexer_instance.ast[i].right, lexer_instance);
+        ret = eval_tree_cd(lexer_instance.ast[i].right, lexer_instance, false);
     }
     return ret;
 }
@@ -190,7 +266,7 @@ void eval(char *cmdline)
         return;
     }
 
-    eval_tree_cd(0, lexer_instance);
+    eval_tree_cd(0, lexer_instance, false);
     return;
 }
 
-- 
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