[newlib-cygwin] Cygwin: Clarify some code in environ.cc

[newlib-cygwin] Cygwin: Clarify some code in environ.cc

[Corinna Vinschen]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=1ecbb8d7b796b980db120d81f625d206c6a728da

commit 1ecbb8d7b796b980db120d81f625d206c6a728da
Author: Ken Brown <kbrown@cornell.edu>
Date:   Wed Jun 6 11:45:54 2018 -0400

    Cygwin: Clarify some code in environ.cc

Diff:
---
 winsup/cygwin/environ.cc | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/winsup/cygwin/environ.cc b/winsup/cygwin/environ.cc
index 4322534..b452d21 100644
--- a/winsup/cygwin/environ.cc
+++ b/winsup/cygwin/environ.cc
@@ -545,6 +545,7 @@ _getenv_r (struct _reent *, const char *name)
   return findenv_func (name, &offset);
 }
 
+/* Return size of environment block, including terminating NULL. */
 static int __stdcall
 envsize (const char * const *in_envp)
 {
@@ -582,11 +583,16 @@ _addenv (const char *name, const char *value, int overwrite)
   else
     {				/* Create new slot. */
       int sz = envsize (cur_environ ());
+
+      /* Allocate space for two new slots even though only one is needed.
+	 According to the commit message for commit ebd645e
+	 (2001-10-03), this is done to "work around problems with some
+	 buggy applications." */
       int allocsz = sz + (2 * sizeof (char *));
 
       offset = (sz - 1) / sizeof (char *);
 
-      /* Allocate space for additional element plus terminating NULL. */
+      /* Allocate space for additional element. */
       if (cur_environ () == lastenviron)
 	lastenviron = __cygwin_environ = (char **) realloc (cur_environ (),
 							    allocsz);