[PATCH 1/2] [gdbsupport] Rewrite handle_eintr

[Tom de Vries]

We have gdb::handle_eintr, which allows us to rewrite:
...
   ssize_t ret;
   do
     {
       errno = 0;
       ret = ::write (pipe[1], "+", 1);
     }
   while (ret == -1 && errno == EINTR);
...
into:
...
   ssize_t ret = gdb::handle_eintr (-1, ::write, pipe[1], "+", 1);
...

However, the call to write got a bit mangled, requiring effort to decode it
back to its original form.

Instead, rewrite gdb::handle_eintr to take a lambda function as parameter,
getting us instead:
...
   ssize_t ret = gdb::handle_eintr<-1> ([&]
     {
       return ::write (pipe[1], "+", 1);
     });
...
where the original call is present.

Tested on aarch64-linux.
---
 gdb/cli/cli-cmds.c      |  5 ++++-
 gdb/nat/linux-waitpid.c |  5 ++++-
 gdbserver/netbsd-low.cc | 25 ++++++++++++++++++++-----
 gdbsupport/eintr.h      | 26 ++++++++++++++------------
 4 files changed, 42 insertions(+), 19 deletions(-)

diff --git a/gdb/cli/cli-cmds.c b/gdb/cli/cli-cmds.c
index 65ac7d6e7fb..3cfc85adf14 100644
--- a/gdb/cli/cli-cmds.c
+++ b/gdb/cli/cli-cmds.c
@@ -923,7 +923,10 @@ run_under_shell (const char *arg, int from_tty)
 
   if (pid != -1)
     {
-      int ret = gdb::handle_eintr (-1, ::waitpid, pid, &status, 0);
+      int ret = gdb::handle_eintr<-1> ([&]
+	{
+	  return ::waitpid (pid, &status, 0);
+	});
       if (ret == -1)
 	perror_with_name ("Cannot get status of shell command");
     }
diff --git a/gdb/nat/linux-waitpid.c b/gdb/nat/linux-waitpid.c
index 0ac2f9fb2b9..6271397b036 100644
--- a/gdb/nat/linux-waitpid.c
+++ b/gdb/nat/linux-waitpid.c
@@ -51,5 +51,8 @@ status_to_str (int status)
 int
 my_waitpid (int pid, int *status, int flags)
 {
-  return gdb::handle_eintr (-1, ::waitpid, pid, status, flags);
+  return gdb::handle_eintr<-1> ([&]
+    {
+      return ::waitpid (pid, status, flags);
+    });
 }
diff --git a/gdbserver/netbsd-low.cc b/gdbserver/netbsd-low.cc
index 4b58826e091..9c6aa9c56ab 100644
--- a/gdbserver/netbsd-low.cc
+++ b/gdbserver/netbsd-low.cc
@@ -222,7 +222,10 @@ netbsd_waitpid (ptid_t ptid, struct target_waitstatus *ourstatus,
   int options = (target_options & TARGET_WNOHANG) ? WNOHANG : 0;
 
   pid_t pid
-    = gdb::handle_eintr (-1, ::waitpid, ptid.pid (), &status, options);
+    = gdb::handle_eintr<-1> ([&]
+      {
+	return ::waitpid (ptid.pid (), &status, options);
+      });
 
   if (pid == -1)
     perror_with_name (_("Child process unexpectedly missing"));
@@ -432,7 +435,10 @@ netbsd_process_target::kill (process_info *process)
     return -1;
 
   int status;
-  if (gdb::handle_eintr (-1, ::waitpid, pid, &status, 0) == -1)
+  if (gdb::handle_eintr<-1> ([&]
+	{
+	  return ::waitpid (pid, &status, 0);
+	}) == -1)
     return -1;
   mourn (process);
   return 0;
@@ -1123,15 +1129,24 @@ netbsd_qxfer_libraries_svr4 (const pid_t pid, const char *annex,
 static bool
 elf_64_file_p (const char *file)
 {
-  int fd = gdb::handle_eintr (-1, ::open, file, O_RDONLY);
+  int fd = gdb::handle_eintr<-1> ([&]
+    {
+      return ::open (file, O_RDONLY);
+    });
   if (fd < 0)
     perror_with_name (("open"));
 
   Elf64_Ehdr header;
-  ssize_t ret = gdb::handle_eintr (-1, ::read, fd, &header, sizeof (header));
+  ssize_t ret = gdb::handle_eintr<-1> ([&]
+    {
+      return ::read (fd, &header, sizeof (header));
+    });
   if (ret == -1)
     perror_with_name (("read"));
-  gdb::handle_eintr (-1, ::close, fd);
+  gdb::handle_eintr<-1> ([&]
+    {
+      return ::close (fd);
+    });
   if (ret != sizeof (header))
     error ("Cannot read ELF file header: %s", file);
 
diff --git a/gdbsupport/eintr.h b/gdbsupport/eintr.h
index e440f935fcf..e08afe1fd9a 100644
--- a/gdbsupport/eintr.h
+++ b/gdbsupport/eintr.h
@@ -43,27 +43,29 @@ namespace gdb
 
    You could wrap it by writing the wrapped form:
 
-   ssize_t ret = gdb::handle_eintr (-1, ::write, pipe[1], "+", 1);
+   ssize_t ret = gdb::handle_eintr<-1> ([&]
+     {
+       return ::write (pipe[1], "+", 1);
+     });
 
    ERRVAL specifies the failure value indicating that the call to the
    F function with ARGS... arguments was possibly interrupted with a
    signal.  */
 
-template<typename ErrorValType, typename Fun, typename... Args>
-inline auto
-handle_eintr (ErrorValType errval, const Fun &f, const Args &... args)
-  -> decltype (f (args...))
+template <auto val, typename F>
+static auto
+handle_eintr (F &&f)
 {
-  decltype (f (args...)) ret;
-
-  do
+  while (true)
     {
       errno = 0;
-      ret = f (args...);
-    }
-  while (ret == errval && errno == EINTR);
 
-  return ret;
+      auto ret = f ();
+      if (ret == val && errno == EINTR)
+	continue;
+
+      return ret;
+    }
 }
 
 } /* namespace gdb */

base-commit: 3d17c8817216343179f64d1a682311a70774ccb4
-- 
2.35.3