gdb::handle_eintr, remove need to specify return type

This eliminates the need to specify the return type when using
handle_eintr.  We let the compiler deduce it for us.

Also, use lowercase for function parameter names.  Uppercase should
only be used on template parameters.

gdb/ChangeLog:

	* nat/linux-waitpid.c: Include "gdbsupport/eintr.h".
	(my_waitpid): Use gdb::handle_eintr.

gdbserver/ChangeLog:

	* netbsd-low.cc (netbsd_waitpid, netbsd_process_target::kill)
	(netbsd_qxfer_libraries_svr4): Use gdb::handle_eintr without
	explicit type.

gdbsupport/ChangeLog:

	* eintr.h (handle_eintr): Replace Ret template parameter with
	ErrorValType.  Use it as type of the failure value.  Deduce the
	function's return type using decltype.  Use lowercase for function
	parameter names.

2 files changed, 22 insertions, 11 deletions

diff --git a/gdbsupport/ChangeLog b/gdbsupport/ChangeLog
index 759eea1..2b01a0b 100644
--- a/gdbsupport/ChangeLog
+++ b/gdbsupport/ChangeLog
@@ -1,3 +1,10 @@
+2020-10-26  Pedro Alves  <pedro@palves.net>
+
+	* eintr.h (handle_eintr): Replace Ret template parameter with
+	ErrorValType.  Use it as type of the failure value.  Deduce the
+	function's return type using decltype.  Use lowercase for function
+	parameter names.
+
 2020-10-25  Simon Marchi  <simon.marchi@polymtl.ca>
 
 	* Makefile.in: Re-generate.
diff --git a/gdbsupport/eintr.h b/gdbsupport/eintr.h
index 64ff594..e097047 100644
--- a/gdbsupport/eintr.h
+++ b/gdbsupport/eintr.h
@@ -43,25 +43,29 @@ namespace gdb
 
    You could wrap it by writing the wrapped form:
 
-   ssize_t ret = gdb::handle_eintr<ssize_t> (-1, ::write, pipe[1], "+", 1);
+   ssize_t ret = gdb::handle_eintr (-1, ::write, pipe[1], "+", 1);
 
-   The RET typename specifies the return type of the wrapped system call, which
-   is typically int or ssize_t.  The R argument specifies the failure value
-   indicating the interrupted syscall when calling the F function with
-   the A... arguments.  */
+   ERRVAL specifies the failure value indicating that the call to the
+   F function with ARGS... arguments was possibly interrupted with a
+   signal.  */
 
-template <typename Ret, typename Fun, typename... Args>
-inline Ret handle_eintr (const Ret &R, const Fun &F, const Args &... A)
+template<typename ErrorValType, typename Fun, typename... Args>
+inline auto
+handle_eintr (ErrorValType errval, const Fun &f, const Args &... args)
+  -> decltype (f (args...))
 {
-  Ret ret;
+  decltype (f (args...)) ret;
+
   do
     {
       errno = 0;
-      ret = F (A...);
+      ret = f (args...);
     }
-  while (ret == R && errno == EINTR);
+  while (ret == errval && errno == EINTR);
+
   return ret;
 }
-}
+
+} /* namespace gdb */
 
 #endif /* GDBSUPPORT_EINTR_H */