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

2 files changed, 28 insertions, 24 deletions

diff --git a/gdbsupport/fileio.cc b/gdbsupport/fileio.cc
index b4feb85..db7c1a7 100644
--- a/gdbsupport/fileio.cc
+++ b/gdbsupport/fileio.cc
@@ -24,7 +24,7 @@
 
 /* See fileio.h.  */
 
-int
+fileio_error
 host_to_fileio_error (int error)
 {
   switch (error)
diff --git a/gdbsupport/fileio.h b/gdbsupport/fileio.h
index 9809c16..6a5297c 100644
--- a/gdbsupport/fileio.h
+++ b/gdbsupport/fileio.h
@@ -67,28 +67,32 @@
 #define FILEIO_SEEK_END             2
 
 /* errno values */
-#define FILEIO_EPERM                1
-#define FILEIO_ENOENT               2
-#define FILEIO_EINTR                4
-#define FILEIO_EIO                  5
-#define FILEIO_EBADF                9
-#define FILEIO_EACCES              13
-#define FILEIO_EFAULT              14
-#define FILEIO_EBUSY               16
-#define FILEIO_EEXIST              17
-#define FILEIO_ENODEV              19
-#define FILEIO_ENOTDIR             20
-#define FILEIO_EISDIR              21
-#define FILEIO_EINVAL              22
-#define FILEIO_ENFILE              23
-#define FILEIO_EMFILE              24
-#define FILEIO_EFBIG               27
-#define FILEIO_ENOSPC              28
-#define FILEIO_ESPIPE              29
-#define FILEIO_EROFS               30
-#define FILEIO_ENOSYS              88
-#define FILEIO_ENAMETOOLONG        91
-#define FILEIO_EUNKNOWN          9999
+enum fileio_error
+{
+  FILEIO_SUCCESS      =    0,
+  FILEIO_EPERM        =    1,
+  FILEIO_ENOENT       =    2,
+  FILEIO_EINTR        =    4,
+  FILEIO_EIO          =    5,
+  FILEIO_EBADF        =    9,
+  FILEIO_EACCES       =   13,
+  FILEIO_EFAULT       =   14,
+  FILEIO_EBUSY        =   16,
+  FILEIO_EEXIST       =   17,
+  FILEIO_ENODEV       =   19,
+  FILEIO_ENOTDIR      =   20,
+  FILEIO_EISDIR       =   21,
+  FILEIO_EINVAL       =   22,
+  FILEIO_ENFILE       =   23,
+  FILEIO_EMFILE       =   24,
+  FILEIO_EFBIG        =   27,
+  FILEIO_ENOSPC       =   28,
+  FILEIO_ESPIPE       =   29,
+  FILEIO_EROFS        =   30,
+  FILEIO_ENOSYS       =   88,
+  FILEIO_ENAMETOOLONG =   91,
+  FILEIO_EUNKNOWN     = 9999,
+};
 
 #define FIO_INT_LEN   4
 #define FIO_UINT_LEN  4
@@ -133,7 +137,7 @@ struct fio_timeval
 
 /* Convert a host-format errno value to a File-I/O error number.  */
 
-extern int host_to_fileio_error (int error);
+extern fileio_error host_to_fileio_error (int error);
 
 /* Convert File-I/O open flags FFLAGS to host format, storing
    the result in *FLAGS.  Return 0 on success, -1 on error.  */