From df19364adef814237b8afd156d3bd1a33d16b318 Mon Sep 17 00:00:00 2001
From: Karen Arutyunov <karen@codesynthesis.com>
Date: Wed, 4 Sep 2024 13:38:49 +0300
Subject: Turn standard streams into blocking mode on start (GH issue 417)

---
 bdep/bdep.cxx | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/bdep/bdep.cxx b/bdep/bdep.cxx
index 02912d0..cc9ac17 100644
--- a/bdep/bdep.cxx
+++ b/bdep/bdep.cxx
@@ -12,6 +12,7 @@
 #include <exception>   // set_terminate(), terminate_handler
 #include <type_traits> // enable_if, is_base_of
 
+#include <libbutl/fdstream.hxx>  // std*_fdmode()
 #include <libbutl/backtrace.hxx> // backtrace()
 
 #include <bdep/types.hxx>
@@ -408,6 +409,24 @@ try
 
   default_terminate = set_terminate (custom_terminate);
 
+  // Note that the standard stream descriptors can potentially be in the
+  // non-blocking mode, which the C++ streams are not suited for and which are
+  // not fully supported by butl::iofdstreams. Using such descriptors may lead
+  // to various weird failures (see GH issue #417 for the reproducer). Thus,
+  // we just turn such descriptors into the blocking mode at the beginning of
+  // the program execution.
+  //
+  try
+  {
+    stdin_fdmode  (fdstream_mode::blocking);
+    stdout_fdmode (fdstream_mode::blocking);
+    stderr_fdmode (fdstream_mode::blocking);
+  }
+  catch (const io_error& e)
+  {
+    fail << "unable to turn standard streams into blocking mode: " << e;
+  }
+
   if (fdterm (stderr_fd ()))
   {
     stderr_term = std::getenv ("TERM");
-- 
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