target.c: fix -Wpointer-sign

$ make WERROR_CFLAGS="-Wpointer-sign -Werror" target.o -k 2>&1 1>/dev/null
../../src/gdb/target.c: In function ‘target_read_stralloc’:
../../src/gdb/target.c:2376:3: error: pointer targets in passing argument 1 of ‘strlen’ differ in signedness [-Werror=pointer-sign]
In file included from build-gnulib/import/string.h:27:0,
                 from ../../src/gdb/common/gdb_string.h:24,
                 from ../../src/gdb/target.c:24:
/usr/include/string.h:399:15: note: expected ‘const char *’ but argument is of type ‘gdb_byte *’
...

This is about the same as the previous patch.

Functions that take or return ascii-ish string arguments usually use
char* for parameters/return.  That means that at points we call into
target methods that work with binary blobs, we need casts to/from
gdb_byte*/char*.  To choose which type for the variables, I usually go
based on which requires the fewer casts, and what the contents of the
variable are supposed to hold, which often gives the same answer.

gdb/
2013-03-07  Pedro Alves  <palves@redhat.com>

	* target.c (target_read_stralloc, target_fileio_read_alloc):
	*Cast pointer to 'gdb_byte *' in target call.

2 files changed, 13 insertions, 6 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 29203fe..da506b4 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,10 @@
 2013-03-07  Pedro Alves  <palves@redhat.com>
 
+	* target.c (target_read_stralloc, target_fileio_read_alloc):
+	*Cast pointer to 'gdb_byte *' in target call.
+
+2013-03-07  Pedro Alves  <palves@redhat.com>
+
 	* corefile.c (read_memory_string): Cast pointer to gdb_byte* in
 	call.
 
diff --git a/gdb/target.c b/gdb/target.c
index ecb1325..eaf8b31 100644
--- a/gdb/target.c
+++ b/gdb/target.c
@@ -2359,10 +2359,11 @@ char *
 target_read_stralloc (struct target_ops *ops, enum target_object object,
 		      const char *annex)
 {
-  gdb_byte *buffer;
+  char *buffer;
   LONGEST i, transferred;
 
-  transferred = target_read_alloc_1 (ops, object, annex, &buffer, 1);
+  transferred = target_read_alloc_1 (ops, object, annex,
+				     (gdb_byte **) &buffer, 1);
 
   if (transferred < 0)
     return NULL;
@@ -2382,7 +2383,7 @@ target_read_stralloc (struct target_ops *ops, enum target_object object,
 	break;
       }
 
-  return (char *) buffer;
+  return buffer;
 }
 
 /* Memory transfer methods.  */
@@ -3522,10 +3523,11 @@ target_fileio_read_alloc (const char *filename, gdb_byte **buf_p)
 char *
 target_fileio_read_stralloc (const char *filename)
 {
-  gdb_byte *buffer;
+  char *buffer;
   LONGEST i, transferred;
 
-  transferred = target_fileio_read_alloc_1 (filename, &buffer, 1);
+  transferred = target_fileio_read_alloc_1 (filename,
+					    (gdb_byte **) &buffer, 1);
 
   if (transferred < 0)
     return NULL;
@@ -3545,7 +3547,7 @@ target_fileio_read_stralloc (const char *filename)
 	break;
       }
 
-  return (char *) buffer;
+  return buffer;
 }