diff --git a/corecheck/tests/Makefile.am b/corecheck/tests/Makefile.am
index 319c8de6e..d1a9ba94f 100644
--- a/corecheck/tests/Makefile.am
+++ b/corecheck/tests/Makefile.am
@@ -1,24 +1 @@
-##---------------------------------------------------------------------------
-## These test core error checking, eg. "silly values" for malloc/calloc,
-## pthread errors (and suppressions), signal handling errors, invalid fds for
-## blocking syscalls, etc.
-##---------------------------------------------------------------------------
-
 noinst_SCRIPTS = filter_stderr
-
-EXTRA_DIST = $(noinst_SCRIPTS) \
-	erringfds.stderr.exp erringfds.stdout.exp erringfds.vgtest \
-	sigkill.stderr.exp sigkill.stderr.exp2 sigkill.vgtest \
-	stack_changes.vgtest
-
-check_PROGRAMS = \
-	erringfds sigkill stack_changes
-
-AM_CFLAGS   = $(WERROR) -Winline -Wall -Wshadow -g -O0
-AM_CPPFLAGS = -I$(top_srcdir)/include
-AM_CXXFLAGS = $(AM_CFLAGS)
-
-sigkill_SOURCES		= sigkill.c
-
-# Stack tests
-stack_changes_SOURCES   = stack_changes.c
diff --git a/corecheck/tests/erringfds.stderr.exp b/corecheck/tests/erringfds.stderr.exp
deleted file mode 100644
index b6a487d38..000000000
--- a/corecheck/tests/erringfds.stderr.exp
+++ /dev/null
@@ -1,4 +0,0 @@
-
-Warning: invalid file descriptor -1 in syscall read()
-
-ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
diff --git a/coregrind/m_errormgr.c b/coregrind/m_errormgr.c
index cf6cfb025..364c38c0d 100644
--- a/coregrind/m_errormgr.c
+++ b/coregrind/m_errormgr.c
@@ -231,6 +231,13 @@ void VG_(set_supp_extra)  ( Supp* su, void* extra )
 /*--- Helper fns                                           ---*/
 /*------------------------------------------------------------*/
 
+// Only show core errors if the tool wants to, we're not running with -q,
+// and were not outputting XML.
+Bool VG_(showing_core_errors)(void)
+{
+   return VG_(needs).core_errors && VG_(clo_verbosity) >= 1 && !VG_(clo_xml);
+}
+
 /* Compare error contexts, to detect duplicates.  Note that if they
    are otherwise the same, the faulting addrs and associated rwoffsets
    are allowed to be different.  */
diff --git a/coregrind/m_signals.c b/coregrind/m_signals.c
index fc66e2370..248d29891 100644
--- a/coregrind/m_signals.c
+++ b/coregrind/m_signals.c
@@ -617,8 +617,7 @@ SysRes VG_(do_sys_sigaction) ( Int signo,
    return VG_(mk_SysRes_Success)( 0 );
 
   bad_signo:
-   if (VG_(needs).core_errors && VG_(clo_verbosity) >= 1
-                              && !VG_(clo_xml)) {
+   if (VG_(showing_core_errors)()) {
       VG_(message)(Vg_UserMsg,
                    "Warning: bad signal number %d in sigaction()", 
                    signo);
@@ -626,8 +625,7 @@ SysRes VG_(do_sys_sigaction) ( Int signo,
    return VG_(mk_SysRes_Error)( VKI_EINVAL );
 
   bad_signo_reserved:
-   if (VG_(needs).core_errors && VG_(clo_verbosity) >= 1
-                              && !VG_(clo_xml)) {
+   if (VG_(showing_core_errors)()) {
       VG_(message)(Vg_UserMsg,
 		   "Warning: ignored attempt to set %s handler in sigaction();",
 		   signame(signo));
@@ -638,8 +636,7 @@ SysRes VG_(do_sys_sigaction) ( Int signo,
    return VG_(mk_SysRes_Error)( VKI_EINVAL );
 
   bad_sigkill_or_sigstop:
-   if (VG_(needs).core_errors && VG_(clo_verbosity) >= 1
-                              && !VG_(clo_xml)) {
+   if (VG_(showing_core_errors)()) {
       VG_(message)(Vg_UserMsg,
 		   "Warning: ignored attempt to set %s handler in sigaction();",
 		   signame(signo));
diff --git a/coregrind/m_syswrap/syswrap-generic.c b/coregrind/m_syswrap/syswrap-generic.c
index cbef16bea..69a793d32 100644
--- a/coregrind/m_syswrap/syswrap-generic.c
+++ b/coregrind/m_syswrap/syswrap-generic.c
@@ -33,6 +33,7 @@
 #include "pub_core_debuginfo.h"     // Needed for pub_core_aspacemgr :(
 #include "pub_core_aspacemgr.h"
 #include "pub_core_debuglog.h"
+#include "pub_core_errormgr.h"
 #include "pub_core_libcbase.h"
 #include "pub_core_libcassert.h"
 #include "pub_core_libcfile.h"
@@ -857,7 +858,9 @@ static Addr do_brk(Addr newbrk)
 /* Return true if we're allowed to use or create this fd */
 Bool ML_(fd_allowed)(Int fd, const Char *syscallname, ThreadId tid, Bool soft)
 {
-   if (fd < 0 || fd >= VG_(fd_hard_limit) || fd == VG_(clo_log_fd)) {
+   if ((fd < 0 || fd >= VG_(fd_hard_limit) || fd == VG_(clo_log_fd)) &&
+       VG_(showing_core_errors)())
+   {
       VG_(message)(Vg_UserMsg, 
          "Warning: invalid file descriptor %d in syscall %s()",
          fd, syscallname);
diff --git a/coregrind/pub_core_errormgr.h b/coregrind/pub_core_errormgr.h
index 4483555b6..bcd1f3b15 100644
--- a/coregrind/pub_core_errormgr.h
+++ b/coregrind/pub_core_errormgr.h
@@ -1,3 +1,4 @@
+
 /*--------------------------------------------------------------------*/
 /*--- ErrorMgr: management of errors and suppressions.             ---*/
 /*---                                          pub_core_errormgr.h ---*/
@@ -55,6 +56,8 @@ extern void VG_(show_error_counts_as_XML) ( void );
 
 extern Bool VG_(is_action_requested)      ( Char* action, Bool* clo );
 
+extern Bool VG_(showing_core_errors)      ( void );
+
 extern UInt VG_(get_n_errs_found)         ( void );
 
 #endif   // __PUB_CORE_ERRORMGR_H
diff --git a/include/pub_tool_tooliface.h b/include/pub_tool_tooliface.h
index 92e413a0f..3482c0103 100644
--- a/include/pub_tool_tooliface.h
+++ b/include/pub_tool_tooliface.h
@@ -130,8 +130,9 @@ extern void VG_(details_bug_reports_to)   ( Char* bug_reports_to );
 extern void VG_(needs_libc_freeres) ( void );
 
 /* Want to have errors detected by Valgrind's core reported?  Includes:
-   - pthread API errors (many;  eg. unlocking a non-locked mutex)
-   - invalid file descriptors to blocking syscalls read() and write()
+   - pthread API errors (many;  eg. unlocking a non-locked mutex) 
+     [currently disabled]
+   - invalid file descriptors to syscalls like read() and write()
    - bad signal numbers passed to sigaction()
    - attempt to install signal handler for SIGKILL or SIGSTOP */
 extern void VG_(needs_core_errors) ( void );
diff --git a/memcheck/tests/Makefile.am b/memcheck/tests/Makefile.am
index bb1537fa1..85d2eed0f 100644
--- a/memcheck/tests/Makefile.am
+++ b/memcheck/tests/Makefile.am
@@ -23,6 +23,7 @@ EXTRA_DIST = $(noinst_SCRIPTS) \
 	custom_alloc.stderr.exp custom_alloc.vgtest \
 	describe-block.stderr.exp describe-block.vgtest \
 	doublefree.stderr.exp doublefree.vgtest \
+	erringfds.stderr.exp erringfds.stdout.exp erringfds.vgtest \
 	error_counts.stderr.exp error_counts.stdout.exp error_counts.vgtest \
 	errs1.stderr.exp errs1.vgtest \
 	exitprog.stderr.exp exitprog.vgtest \
@@ -65,8 +66,10 @@ EXTRA_DIST = $(noinst_SCRIPTS) \
 	realloc2.stderr.exp realloc2.vgtest \
 	realloc3.stderr.exp realloc3.vgtest \
 	sigaltstack.stderr.exp sigaltstack.vgtest \
+	sigkill.stderr.exp sigkill.stderr.exp2 sigkill.vgtest \
 	signal2.stderr.exp signal2.stdout.exp signal2.vgtest \
 	sigprocmask.stderr.exp sigprocmask.vgtest \
+	stack_changes.stderr.exp stack_changes.stdout.exp stack_changes.vgtest \
 	strchr.stderr.exp strchr.vgtest \
 	str_tester.stderr.exp str_tester.vgtest \
 	supp1.stderr.exp supp1.vgtest \
@@ -88,7 +91,7 @@ check_PROGRAMS = \
 	badloop badpoll badrw brk brk2 buflen_check \
 	clientperm custom_alloc \
 	describe-block \
-	doublefree error_counts errs1 exitprog execve execve2 \
+	doublefree error_counts errs1 exitprog execve execve2 erringfds \
 	fprw fwrite hello inits inline \
 	leak-0 leak-cycle leak-tree leak-regroot leakotron \
 	malloc1 malloc2 malloc3 manuel1 manuel2 manuel3 \
@@ -99,8 +102,8 @@ check_PROGRAMS = \
 	pointer-trace \
 	post-syscall \
 	realloc1 realloc2 realloc3 \
-	sigaltstack signal2 sigprocmask \
-	strchr str_tester supp1 supp2 suppfree \
+	sigaltstack signal2 sigprocmask sigkill \
+	stack_changes strchr str_tester supp1 supp2 suppfree \
 	trivialleak weirdioctl	\
 	mismatches new_override metadata \
 	vgtest_ume xml1 \
@@ -112,18 +115,18 @@ AM_CFLAGS   = $(WERROR) -Winline -Wall -Wshadow -g
 AM_CXXFLAGS = $(AM_CFLAGS)
 
 # C ones
-addressable_SOURCES	= addressable.c
-badaddrvalue_SOURCES 	= badaddrvalue.c
-badfree_SOURCES 	= badfree.c
-badjump_SOURCES 	= badjump.c
-badjump2_SOURCES 	= badjump2.c
-badloop_SOURCES 	= badloop.c
-badpoll_SOURCES		= badpoll.c
-badrw_SOURCES		= badrw.c
-brk_SOURCES 		= brk.c
-brk2_SOURCES 		= brk2.c
-buflen_check_SOURCES	= buflen_check.c
-clientperm_SOURCES 	= clientperm.c
+#addressable_SOURCES	= addressable.c
+#badaddrvalue_SOURCES 	= badaddrvalue.c
+#badfree_SOURCES 	= badfree.c
+#badjump_SOURCES 	= badjump.c
+#badjump2_SOURCES 	= badjump2.c
+#badloop_SOURCES 	= badloop.c
+#badpoll_SOURCES		= badpoll.c
+#badrw_SOURCES		= badrw.c
+#brk_SOURCES 		= brk.c
+#brk2_SOURCES 		= brk2.c
+#buflen_check_SOURCES	= buflen_check.c
+#clientperm_SOURCES 	= clientperm.c
 custom_alloc_SOURCES 	= custom_alloc.c
 describe_block_SOURCES	= describe-block.c
 doublefree_SOURCES 	= doublefree.c
@@ -159,13 +162,15 @@ null_socket_SOURCES 	= null_socket.c
 overlap_SOURCES 	= overlap.c
 # Don't allow GCC to inline memcpy(), because then we can't intercept it
 overlap_CFLAGS		= $(AM_CFLAGS) -fno-builtin-memcpy
-pointer_trace_SOURCES	= pointer-trace.c
+#pointer_trace_SOURCES	= pointer-trace.c
 post_syscall_SOURCES	= post-syscall.c
 realloc1_SOURCES 	= realloc1.c
 realloc2_SOURCES 	= realloc2.c
 realloc3_SOURCES 	= realloc3.c
+sigkill_SOURCES		= sigkill.c
 signal2_SOURCES 	= signal2.c
 sigprocmask_SOURCES 	= sigprocmask.c
+stack_changes_SOURCES   = stack_changes.c
 supp1_SOURCES 		= supp.c
 supp2_SOURCES 		= supp.c
 suppfree_SOURCES 	= suppfree.c
diff --git a/corecheck/tests/erringfds.c b/memcheck/tests/erringfds.c
similarity index 100%
rename from corecheck/tests/erringfds.c
rename to memcheck/tests/erringfds.c
diff --git a/memcheck/tests/erringfds.stderr.exp b/memcheck/tests/erringfds.stderr.exp
new file mode 100644
index 000000000..0516e0908
--- /dev/null
+++ b/memcheck/tests/erringfds.stderr.exp
@@ -0,0 +1,8 @@
+
+Warning: invalid file descriptor -1 in syscall read()
+
+ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
+malloc/free: in use at exit: 0 bytes in 0 blocks.
+malloc/free: 0 allocs, 0 frees, 0 bytes allocated.
+For a detailed leak analysis,  rerun with: --leak-check=yes
+For counts of detected errors, rerun with: -v
diff --git a/corecheck/tests/erringfds.stdout.exp b/memcheck/tests/erringfds.stdout.exp
similarity index 100%
rename from corecheck/tests/erringfds.stdout.exp
rename to memcheck/tests/erringfds.stdout.exp
diff --git a/corecheck/tests/erringfds.vgtest b/memcheck/tests/erringfds.vgtest
similarity index 100%
rename from corecheck/tests/erringfds.vgtest
rename to memcheck/tests/erringfds.vgtest
diff --git a/corecheck/tests/sigkill.c b/memcheck/tests/sigkill.c
similarity index 100%
rename from corecheck/tests/sigkill.c
rename to memcheck/tests/sigkill.c
diff --git a/corecheck/tests/sigkill.stderr.exp b/memcheck/tests/sigkill.stderr.exp
similarity index 94%
rename from corecheck/tests/sigkill.stderr.exp
rename to memcheck/tests/sigkill.stderr.exp
index b71799dda..7dbb0d48f 100644
--- a/corecheck/tests/sigkill.stderr.exp
+++ b/memcheck/tests/sigkill.stderr.exp
@@ -196,3 +196,7 @@ Invalid argument
 
 
 ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
+malloc/free: in use at exit: 0 bytes in 0 blocks.
+malloc/free: 0 allocs, 0 frees, 0 bytes allocated.
+For a detailed leak analysis,  rerun with: --leak-check=yes
+For counts of detected errors, rerun with: -v
diff --git a/corecheck/tests/sigkill.stderr.exp2 b/memcheck/tests/sigkill.stderr.exp2
similarity index 94%
rename from corecheck/tests/sigkill.stderr.exp2
rename to memcheck/tests/sigkill.stderr.exp2
index 896213faa..3cc35594a 100644
--- a/corecheck/tests/sigkill.stderr.exp2
+++ b/memcheck/tests/sigkill.stderr.exp2
@@ -196,3 +196,7 @@ Invalid argument
 
 
 ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
+malloc/free: in use at exit: 0 bytes in 0 blocks.
+malloc/free: 0 allocs, 0 frees, 0 bytes allocated.
+For a detailed leak analysis,  rerun with: --leak-check=yes
+For counts of detected errors, rerun with: -v
diff --git a/corecheck/tests/sigkill.stderr.exp3 b/memcheck/tests/sigkill.stderr.exp3
similarity index 94%
rename from corecheck/tests/sigkill.stderr.exp3
rename to memcheck/tests/sigkill.stderr.exp3
index a538a530f..dfe65480d 100644
--- a/corecheck/tests/sigkill.stderr.exp3
+++ b/memcheck/tests/sigkill.stderr.exp3
@@ -196,3 +196,7 @@ Invalid argument
 
 
 ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
+malloc/free: in use at exit: 0 bytes in 0 blocks.
+malloc/free: 0 allocs, 0 frees, 0 bytes allocated.
+For a detailed leak analysis,  rerun with: --leak-check=yes
+For counts of detected errors, rerun with: -v
diff --git a/corecheck/tests/sigkill.vgtest b/memcheck/tests/sigkill.vgtest
similarity index 100%
rename from corecheck/tests/sigkill.vgtest
rename to memcheck/tests/sigkill.vgtest
diff --git a/corecheck/tests/stack_changes.c b/memcheck/tests/stack_changes.c
similarity index 100%
rename from corecheck/tests/stack_changes.c
rename to memcheck/tests/stack_changes.c
diff --git a/corecheck/tests/stack_changes.stderr.exp b/memcheck/tests/stack_changes.stderr.exp
similarity index 100%
rename from corecheck/tests/stack_changes.stderr.exp
rename to memcheck/tests/stack_changes.stderr.exp
diff --git a/corecheck/tests/stack_changes.stdout.exp b/memcheck/tests/stack_changes.stdout.exp
similarity index 100%
rename from corecheck/tests/stack_changes.stdout.exp
rename to memcheck/tests/stack_changes.stdout.exp
diff --git a/corecheck/tests/stack_changes.vgtest b/memcheck/tests/stack_changes.vgtest
similarity index 100%
rename from corecheck/tests/stack_changes.vgtest
rename to memcheck/tests/stack_changes.vgtest