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PR18617 - Incorrect expression bytecode generated for narrowing conversions

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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.
This commit is contained in:
Robert O'Callahan
2015-07-08 11:11:22 +01:00
committed by Pedro Alves
parent 7201f0e83a
commit cc1259417e
4 changed files with 13 additions and 1 deletions
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5
gdb/ChangeLog
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@@ -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'.
2015-07-06 Joel Brobecker <brobecker@adacore.com>
* version.in: Set GDB version number to 7.9.90.DATE-cvs.

2
gdb/ax-gdb.c
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@@ -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. */

5
gdb/testsuite/ChangeLog
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@@ -1,3 +1,8 @@
2015-07-08 Robert O'Callahan <robert@ocallahan.org>
PR exp/18617
* gdb.trace/ax.exp: Add test.
2015-06-30 Martin Galvan <martin.galvan@tallertechnologies.com>
* lib/gdb.exp (test_class_help): Remove the unneeded escaping of

2
gdb/testsuite/gdb.trace/ax.exp
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@@ -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"