handle terminal resize while running external program

Author: d99kris

src/nmail.1

@@ -1,5 +1,5 @@
 .\" DO NOT MODIFY THIS FILE!  It was generated by help2man.
-.TH NMAIL "1" "February 2026" "nmail 5.11.4" "User Commands"
+.TH NMAIL "1" "March 2026" "nmail 5.12.1" "User Commands"
 .SH NAME
 nmail \- ncurses mail
 .SH SYNOPSIS

src/util.cpp

@@ -8,6 +8,7 @@
 #include "util.h"
 
 #include <algorithm>
+#include <cerrno>
 #include <csignal>
 #include <cstring>
 #include <fstream>
@@ -2336,15 +2337,52 @@ int Util::System(const std::string& p_Cmd)
   static const std::string shPath = "/bin/sh";
 #endif
 
+  // Block SIGCHLD and ignore SIGINT/SIGQUIT in parent per POSIX system() spec
+  struct sigaction saIgnore;
+  struct sigaction saOrigInt;
+  struct sigaction saOrigQuit;
+  saIgnore.sa_handler = SIG_IGN;
+  sigemptyset(&saIgnore.sa_mask);
+  saIgnore.sa_flags = 0;
+  sigaction(SIGINT, &saIgnore, &saOrigInt);
+  sigaction(SIGQUIT, &saIgnore, &saOrigQuit);
+
+  sigset_t blockChld;
+  sigset_t origMask;
+  sigemptyset(&blockChld);
+  sigaddset(&blockChld, SIGCHLD);
+  sigprocmask(SIG_BLOCK, &blockChld, &origMask);
+
   pid_t pid = fork();
   if (pid == 0)
   {
+    // Child: restore original signal dispositions and mask
+    sigaction(SIGINT, &saOrigInt, nullptr);
+    sigaction(SIGQUIT, &saOrigQuit, nullptr);
+    sigprocmask(SIG_SETMASK, &origMask, nullptr);
+
     execl(shPath.c_str(), "sh", "-c", p_Cmd.c_str(), (char*)nullptr);
     _exit(127);
   }
 
-  if (pid < 0) return -1;
+  int status = -1;
+  if (pid > 0)
+  {
+    // Retry waitpid on EINTR (e.g. from SIGWINCH during terminal resize)
+    while (waitpid(pid, &status, 0) < 0)
+    {
+      if (errno != EINTR)
+      {
+        status = -1;
+        break;
+      }
+    }
+  }
+
+  // Restore original signal dispositions and mask
+  sigaction(SIGINT, &saOrigInt, nullptr);
+  sigaction(SIGQUIT, &saOrigQuit, nullptr);
+  sigprocmask(SIG_SETMASK, &origMask, nullptr);
 
-  int status = 0;
-  return (waitpid(pid, &status, 0) < 0) ? -1 : status;
+  return status;
 }

src/version.cpp

@@ -7,7 +7,7 @@
 
 #include "version.h"
 
-#define NMAIL_VERSION "5.11.4"
+#define NMAIL_VERSION "5.12.1"
 
 std::string Version::GetBuildOs()
 {