clang -fsanitize=undefined error in ecpg

With clang -fsanitize=undefined (clang-3.4), I get the following test failure in ecpg
(it's the only one in the entire tree):

--- a/src/interfaces/ecpg/test/expected/pgtypeslib-dt_test2.stderr
+++ b/src/interfaces/ecpg/test/results/pgtypeslib-dt_test2.stderr
@@ -1,2 +1,4 @@
[NO_PID]: ECPGdebug: set to 1
[NO_PID]: sqlca: code: 0, state: 00000
+dt_common.c:2209:13: runtime error: left shift of 1 by 31 places cannot be represented in type 'int'
+dt_common.c:1424:12: runtime error: left shift of 1 by 31 places cannot be represented in type 'int'

This happens while parsing these strings:

"19990108foobar"
"19990108 foobar",
"1999-01-08 foobar"
"........................Xaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"

(I'm not sure why it reports two warnings for four cases. Maybe it collapses some warnings.)

This patch fixes it:

diff --git a/src/interfaces/ecpg/pgtypeslib/dt.h b/src/interfaces/ecpg/pgtypeslib/dt.h
index 145e2b7..2ccd0be 100644
--- a/src/interfaces/ecpg/pgtypeslib/dt.h
+++ b/src/interfaces/ecpg/pgtypeslib/dt.h
@@ -193,7 +193,7 @@ typedef double fsec_t;
* Bit mask definitions for time parsing.
*/
/* Copy&pasted these values from src/include/utils/datetime.h */
-#define DTK_M(t) (0x01 << (t))
+#define DTK_M(t) ((t) == UNKNOWN_FIELD ? 0 : 0x01 << (t))
#define DTK_ALL_SECS_M (DTK_M(SECOND) | DTK_M(MILLISECOND) | DTK_M(MICROSECOND))
#define DTK_DATE_M (DTK_M(YEAR) | DTK_M(MONTH) | DTK_M(DAY))
#define DTK_TIME_M (DTK_M(HOUR) | DTK_M(MINUTE) | DTK_M(SECOND))

Strangely, I cannot reproduce this failure with the backend datetime code that
this was supposedly copied from.

Comments?