gdbsupport: convert FILEIO_* macros to an enum

Converting from free-form macros to an enum gives a bit of type-safety.
This caught places where we would assign host error numbers to what
should contain a target fileio error number, for instance in
target_fileio_pread.

I added the FILEIO_SUCCESS enumerator, because
remote.c:remote_hostio_parse_result initializes the remote_errno output
variable to 0.  It seems better to have an explicit enumerator than to
assign a value for which there is no enumerator.  I considered
initializing this variable to FILEIO_EUNKNOWN instead, such that if the
remote side replies with an error and omits the errno value, we'll get
an errno that represents an error instead of 0 (which reprensents no
error).  But it's not clear what the consequences of that change would
be, so I prefer to err on the side of caution and just keep the existing
behavior (there is no intended change in behavior with this patch).

Note that remote_hostio_parse_resul still reads blindly what the remote
side sends as a target errno into this variable, so we can still end up
with a nonsensical value here.  It's not good, but out of the scope of
this patch.

Convert host_to_fileio_error and fileio_errno_to_host to return / accept
a fileio_error instead of an int, and cascade the change in the whole
chain that uses that.

Change-Id: I454b0e3fcf0732447bc872252fa8e57d138b0e03

1 files changed, 6 insertions, 5 deletions

diff --git a/gdb/gdb_bfd.c b/gdb/gdb_bfd.c
index 7631e27..1438815 100644
--- a/gdb/gdb_bfd.c
+++ b/gdb/gdb_bfd.c
@@ -306,7 +306,7 @@ gdb_bfd_open_from_target_memory (CORE_ADDR addr, ULONGEST size,
 /* Return the system error number corresponding to ERRNUM.  */
 
 static int
-fileio_errno_to_host (int errnum)
+fileio_errno_to_host (fileio_error errnum)
 {
   switch (errnum)
     {
@@ -370,7 +370,8 @@ static void *
 gdb_bfd_iovec_fileio_open (struct bfd *abfd, void *open_closure)
 {
   const char *filename = bfd_get_filename (abfd);
-  int fd, target_errno;
+  int fd;
+  fileio_error target_errno;
   int *stream;
   gdb_bfd_open_closure *oclosure = (gdb_bfd_open_closure *) open_closure;
 
@@ -400,7 +401,7 @@ gdb_bfd_iovec_fileio_pread (struct bfd *abfd, void *stream, void *buf,
 			    file_ptr nbytes, file_ptr offset)
 {
   int fd = *(int *) stream;
-  int target_errno;
+  fileio_error target_errno;
   file_ptr pos, bytes;
 
   pos = 0;
@@ -443,7 +444,7 @@ static int
 gdb_bfd_iovec_fileio_close (struct bfd *abfd, void *stream)
 {
   int fd = *(int *) stream;
-  int target_errno;
+  fileio_error target_errno;
 
   xfree (stream);
 
@@ -472,7 +473,7 @@ gdb_bfd_iovec_fileio_fstat (struct bfd *abfd, void *stream,
 			    struct stat *sb)
 {
   int fd = *(int *) stream;
-  int target_errno;
+  fileio_error target_errno;
   int result;
 
   result = target_fileio_fstat (fd, sb, &target_errno);