target_read_memory&co: no longer return target_xfer_status

Years ago, these functions used to return errno/EIO.  Later, through a
series of changes that intended to remove native/remote differences,
they ended up returning a target_xfer_status in disguise.

Unlike target_xfer_partial&co, the point of target_read_memory&co is
to either fully succeed or fail.  On error, they always return
TARGET_XFER_E_IO.  So there's no real point in casting the return of
target_read_memory to a target_xfer_status to pass it to memory_error.
Instead, it results in clearer code to simply decouple
target_read_memory&co's return from target_xfer_status.

This fixes build errors like this in C++ mode:

 ../../src/gdb/corefile.c: In function ‘void read_stack(CORE_ADDR, gdb_byte*, ssize_t)’:
 ../../src/gdb/corefile.c:276:34: error: invalid conversion from ‘int’ to ‘target_xfer_status’ [-fpermissive]
      memory_error (status, memaddr);
				   ^
 ../../src/gdb/corefile.c:216:1: error:   initializing argument 1 of ‘void memory_error(target_xfer_status, CORE_ADDR)’ [-fpermissive]

gdb/ChangeLog:
2015-10-27  Pedro Alves  <palves@redhat.com>

	* alpha-tdep.c (alpha_read_insn): Always pass TARGET_XFER_E_IO to
	memory_error.  Rename local 'status' to 'res'.
	* c-lang.c (c_get_string): Always pass TARGET_XFER_E_IO to
	memory_error.
	* corefile.c (read_stack, read_code, write_memory): Always pass
	TARGET_XFER_E_IO to memory_error.
	* disasm.c (dis_asm_memory_error): Always pass TARGET_XFER_E_IO to
	memory_error.  Rename parameter 'status' to 'err'.
	(dump_insns): Rename local 'status' to 'err'.
	* mips-tdep.c (mips_fetch_instruction): Rename parameter 'statusp'
	to 'errp'.  Rename local 'status' to 'err'.  Always pass
	TARGET_XFER_E_IO to memory_error.
	(mips_breakpoint_from_pc): Rename local 'status' to 'err'.
	* target.c (target_read_memory, target_read_raw_memory)
	(target_read_stack, target_read_code, target_write_memory)
	(target_write_raw_memory): Return -1 on error instead of
	TARGET_XFER_E_IO.
	* valprint.c (val_print_string): Rename local 'errcode' to 'err'.
	Always pass TARGET_XFER_E_IO to memory_error.  Update comment.

1 files changed, 7 insertions, 7 deletions

diff --git a/gdb/valprint.c b/gdb/valprint.c
index 7e74856..7f891c9 100644
--- a/gdb/valprint.c
+++ b/gdb/valprint.c
@@ -2737,7 +2737,7 @@ val_print_string (struct type *elttype, const char *encoding,
 		  const struct value_print_options *options)
 {
   int force_ellipsis = 0;	/* Force ellipsis to be printed if nonzero.  */
-  int errcode;			/* Errno returned from bad reads.  */
+  int err;			/* Non-zero if we got a bad read.  */
   int found_nul;		/* Non-zero if we found the nul char.  */
   unsigned int fetchlimit;	/* Maximum number of chars to print.  */
   int bytes_read;
@@ -2758,8 +2758,8 @@ val_print_string (struct type *elttype, const char *encoding,
   fetchlimit = (len == -1 ? options->print_max : min (len,
 						      options->print_max));
 
-  errcode = read_string (addr, len, width, fetchlimit, byte_order,
-			 &buffer, &bytes_read);
+  err = read_string (addr, len, width, fetchlimit, byte_order,
+		     &buffer, &bytes_read);
   old_chain = make_cleanup (xfree, buffer);
 
   addr += bytes_read;
@@ -2787,7 +2787,7 @@ val_print_string (struct type *elttype, const char *encoding,
 	  && extract_unsigned_integer (peekbuf, width, byte_order) != 0)
 	force_ellipsis = 1;
     }
-  else if ((len >= 0 && errcode != 0) || (len > bytes_read / width))
+  else if ((len >= 0 && err != 0) || (len > bytes_read / width))
     {
       /* Getting an error when we have a requested length, or fetching less
          than the number of characters actually requested, always make us
@@ -2798,17 +2798,17 @@ val_print_string (struct type *elttype, const char *encoding,
   /* If we get an error before fetching anything, don't print a string.
      But if we fetch something and then get an error, print the string
      and then the error message.  */
-  if (errcode == 0 || bytes_read > 0)
+  if (err == 0 || bytes_read > 0)
     {
       LA_PRINT_STRING (stream, elttype, buffer, bytes_read / width,
 		       encoding, force_ellipsis, options);
     }
 
-  if (errcode != 0)
+  if (err != 0)
     {
       char *str;
 
-      str = memory_error_message (errcode, gdbarch, addr);
+      str = memory_error_message (TARGET_XFER_E_IO, gdbarch, addr);
       make_cleanup (xfree, str);
 
       fprintf_filtered (stream, "<error: ");