[PATCH] Tweak gdb.trace/tfile.c for thumb mode

[Yao Qi <yao@codesourcery.com>]

We see the fail below happens on thumb related multi-libs
(-mthumb -march={armv4t,armv7-a}),

target tfile tfile-basic.tf ^M
warning: Uploaded tracepoint 1 has no source location, using raw address^M
warning: Breakpoint address adjusted from 0x00008959 to 0x00008958.^M
Tracepoint 3 at 0x8958: file /scratch/yqi/arm-none-linux-gnueabi/src/gdb-trunk/gdb/testsuite/gdb.trace/tfile.c, line 91.^M
Created tracepoint 3 for target's tracepoint 1 at 0x8959.^M
warning: Breakpoint address adjusted from 0x00008959 to 0x00008958.^M
warning: Breakpoint address adjusted from 0x00008959 to 0x00008958.^M
warning: Breakpoint address adjusted from 0x00008959 to 0x00008958.^M
(gdb) FAIL: gdb.trace/tfile.exp: complete-command 'target tfile'

The address of write_basic_trace_file is two-bytes aligned,

(gdb) p write_basic_trace_file
$1 = {void (void)} 0x8958 <write_basic_trace_file>

but the ld sets the LSB of every reference to the function address
(indicating the address is in thumb mode), so "&write_basic_trace_file"
in the program becomes 0x8959, which is saved in the trace file.  That
is why the warnings are emitted.

This patch is to clear the LSB of the function address written to trace
file in thumb and thumb2 mode.  This patch fixes the fail above.

gdb/testsuite:

2014-06-30  Yao Qi  <yao@codesourcery.com>

	* gdb.trace/tfile.c (write_basic_trace_file): Clear the lsb of
	the function address written to trace file.
---
 gdb/testsuite/gdb.trace/tfile.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/gdb/testsuite/gdb.trace/tfile.c b/gdb/testsuite/gdb.trace/tfile.c
index ac65901..4d54553 100644
--- a/gdb/testsuite/gdb.trace/tfile.c
+++ b/gdb/testsuite/gdb.trace/tfile.c
@@ -91,6 +91,7 @@ write_basic_trace_file (void)
 {
   int fd, int_x;
   short short_x;
+  long func_addr;
 
   fd = start_trace_file (TFILE_DIR "tfile-basic.tf");
 
@@ -109,8 +110,14 @@ write_basic_trace_file (void)
   /* Dump tracepoint definitions, in syntax similar to that used
      for reconnection uploads.  */
   /* FIXME need a portable way to print function address in hex */
-  snprintf (spbuf, sizeof spbuf, "tp T1:%lx:E:0:0\n",
-	    (long) &write_basic_trace_file);
+  func_addr = (long) &write_basic_trace_file;
+  /* Although the thumb functions are two-bytes aligned, ld sets the
+     bit 0 of these function references.  Clear the bit 0.  */
+#if defined(__thumb__) || defined(__thumb2__)
+  func_addr &= ~1;
+#endif
+
+  snprintf (spbuf, sizeof spbuf, "tp T1:%lx:E:0:0\n", func_addr);
   write (fd, spbuf, strlen (spbuf));
   /* (Note that we would only need actions defined if we wanted to
      test tdump.) */
-- 
1.9.0