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, 13 insertions, 12 deletions

diff --git a/gdb/mips-tdep.c b/gdb/mips-tdep.c
index 7cea832..6b5a1bd 100644
--- a/gdb/mips-tdep.c
+++ b/gdb/mips-tdep.c
@@ -1429,12 +1429,12 @@ mips_write_pc (struct regcache *regcache, CORE_ADDR pc)
 
 static ULONGEST
 mips_fetch_instruction (struct gdbarch *gdbarch,
-			enum mips_isa isa, CORE_ADDR addr, int *statusp)
+			enum mips_isa isa, CORE_ADDR addr, int *errp)
 {
   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
   gdb_byte buf[MIPS_INSN32_SIZE];
   int instlen;
-  int status;
+  int err;
 
   switch (isa)
     {
@@ -1450,13 +1450,13 @@ mips_fetch_instruction (struct gdbarch *gdbarch,
       internal_error (__FILE__, __LINE__, _("invalid ISA"));
       break;
     }
-  status = target_read_memory (addr, buf, instlen);
-  if (statusp != NULL)
-    *statusp = status;
-  if (status)
+  err = target_read_memory (addr, buf, instlen);
+  if (errp != NULL)
+    *errp = err;
+  if (err != 0)
     {
-      if (statusp == NULL)
-	memory_error (status, addr);
+      if (errp == NULL)
+	memory_error (TARGET_XFER_E_IO, addr);
       return 0;
     }
   return extract_unsigned_integer (buf, instlen, byte_order);
@@ -7118,12 +7118,13 @@ mips_breakpoint_from_pc (struct gdbarch *gdbarch,
 	  static gdb_byte micromips16_big_breakpoint[] = { 0x46, 0x85 };
 	  static gdb_byte micromips32_big_breakpoint[] = { 0, 0x5, 0, 0x7 };
 	  ULONGEST insn;
-	  int status;
+	  int err;
 	  int size;
 
-	  insn = mips_fetch_instruction (gdbarch, ISA_MICROMIPS, pc, &status);
-	  size = status ? 2
-			: mips_insn_size (ISA_MICROMIPS, insn) == 2 ? 2 : 4;
+	  insn = mips_fetch_instruction (gdbarch, ISA_MICROMIPS, pc, &err);
+	  size = (err != 0
+		  ? 2 : (mips_insn_size (ISA_MICROMIPS, insn) == 2
+			 ? 2 : 4));
 	  *pcptr = unmake_compact_addr (pc);
 	  *lenptr = size;
 	  return (size == 2) ? micromips16_big_breakpoint