PR18617 - Incorrect expression bytecode generated for narrowing conversions

The existing code preserves 'from' bits, which is incorrect.  E.g.

 (gdb) maint agent-eval (char)255L
 Scope: 0x4008d6
 Reg mask: 00
   0  const16 255
   3  ext 64
   5  end

'ext 64' should be 'ext 8'; this bytecode evaluates to 255 instead of
the correct result of -1.  The fix is simple.  I ran the entire test
suite on x86-64 and there were no new test failures.

gdb/ChangeLog:
2015-07-08  Robert O'Callahan  <robert@ocallahan.org>

	PR exp/18617
	* ax-gdb.c (gen_conversion): Extend to 'to' bits, not 'from'.

gdb/testsuite/ChangeLog:
2015-07-08  Robert O'Callahan  <robert@ocallahan.org>

	PR exp/18617
	* gdb.trace/ax.exp: Add test.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index de4ca2e..723ed2c 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2015-07-08  Robert O'Callahan  <robert@ocallahan.org>
+
+       PR exp/18617
+       * ax-gdb.c (gen_conversion): Extend to 'to' bits, not 'from'.
+
 2015-07-08  Markus Metzger  <markus.t.metzger@intel.com>
 
        * MAINTAINERS (Write After Approval): Add Markus T. Metzger.

diff --git a/gdb/ax-gdb.c b/gdb/ax-gdb.c
index 7a9d1e7..38dacac 100644 (file)
--- a/gdb/ax-gdb.c
+++ b/gdb/ax-gdb.c
@@ -885,7 +885,7 @@ gen_conversion (struct agent_expr *ax, struct type *from, struct type *to)
   /* If we're converting to a narrower type, then we need to clear out
      the upper bits.  */
   if (TYPE_LENGTH (to) < TYPE_LENGTH (from))
-    gen_extend (ax, from);
+    gen_extend (ax, to);
 
   /* If the two values have equal width, but different signednesses,
      then we need to extend.  */

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index c5386b2..285bf2c 100644 (file)
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2015-07-08  Robert O'Callahan  <robert@ocallahan.org>
+
+       PR exp/18617
+       * gdb.trace/ax.exp: Add test.
+
 2015-07-07  Yao Qi  <yao.qi@linaro.org>
 
        * gdb.arch/aarch64-atomic-inst.exp: Check is_aarch64_target

diff --git a/gdb/testsuite/gdb.trace/ax.exp b/gdb/testsuite/gdb.trace/ax.exp
index e3d0479..d064475 100644 (file)
--- a/gdb/testsuite/gdb.trace/ax.exp
+++ b/gdb/testsuite/gdb.trace/ax.exp
@@ -80,6 +80,8 @@ gdb_test "maint agent &gdb_long_test == &gdb_short_test" "" "maint agent &gdb_lo
 
 gdb_test "maint agent &gdb_long_test < &gdb_short_test" "" "maint agent &gdb_long_test < &gdb_short_test"
 
+gdb_test "maint agent (unsigned char)1L" ".*ext 8.*" "maint agent (unsigned char)1L"
+
 # Now test eval version of agent expressions.
 
 gdb_test "maint agent-eval 12" ".*const8 12.*end.*" "maint agent-eval 12"