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Re: [Qemu-devel] [RFC PATCH] osdep.h: Prohibit disabling assert() in sup


From: Philippe Mathieu-Daudé
Subject: Re: [Qemu-devel] [RFC PATCH] osdep.h: Prohibit disabling assert() in supported builds
Date: Fri, 18 Aug 2017 19:57:27 -0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1

On 08/18/2017 07:23 PM, Eric Blake wrote:
We already have several files that knowingly require assert()
to work.  While we do NOT want to encourage the use of
'assert(side-effects)' (that is a bad practice that prevents
copy-and-paste of code to other projects that CAN disable
assertions; plus it costs unnecessary reviewer mental cycles
to remember our project policy on crippling asserts), we DO
want to send a message that anyone that disables assertions
has to tweak code in order to compile, making it obvious that
we are not going to support their efforts.

Signed-off-by: Eric Blake <address@hidden>
---

First mentioned as an idea here:
http://lists.nongnu.org/archive/html/qemu-devel/2017-07/msg06084.html
but I'm titling this RFC as I'm not 100% convinced we want to make
it a project-wide, rather than a per-file decision.

I think project-wide is the correct way.

Reviewed-by: Philippe Mathieu-Daudé <address@hidden>


  include/qemu/osdep.h | 12 ++++++++++++
  hw/scsi/mptsas.c     |  4 ----
  hw/virtio/virtio.c   |  4 ----
  3 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index 6855b94bbf..9e745a8af9 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -107,6 +107,18 @@ extern int daemon(int, int);
  #include "glib-compat.h"
  #include "qemu/typedefs.h"

+/*
+ * We have a lot of unaudited code that will fail in strange ways if
+ * you disable assertions at compile-time.  You are on your own if
+ * you cripple these safety-checks.
+ */
+#ifdef NDEBUG
+#error building with NDEBUG is not supported
+#endif
+#ifdef G_DISABLE_ASSERT
+#error building with G_DISABLE_ASSERT is not supported
+#endif
+
  #ifndef O_LARGEFILE
  #define O_LARGEFILE 0
  #endif
diff --git a/hw/scsi/mptsas.c b/hw/scsi/mptsas.c
index 765ab53c34..3b93f12cdb 100644
--- a/hw/scsi/mptsas.c
+++ b/hw/scsi/mptsas.c
@@ -1236,11 +1236,7 @@ static void *mptsas_load_request(QEMUFile *f, 
SCSIRequest *sreq)
      n = qemu_get_be32(f);
      /* TODO: add a way for SCSIBusInfo's load_request to fail,
       * and fail migration instead of asserting here.
-     * When we do, we might be able to re-enable NDEBUG below.
       */
-#ifdef NDEBUG
-#error building with NDEBUG is not supported
-#endif
      assert(n >= 0);

      pci_dma_sglist_init(&req->qsg, pci, n);
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 464947f76d..2778adabcc 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -1025,11 +1025,7 @@ void *qemu_get_virtqueue_element(VirtIODevice *vdev, 
QEMUFile *f, size_t sz)

      /* TODO: teach all callers that this can fail, and return failure instead
       * of asserting here.
-     * When we do, we might be able to re-enable NDEBUG below.
       */
-#ifdef NDEBUG
-#error building with NDEBUG is not supported
-#endif
      assert(ARRAY_SIZE(data.in_addr) >= data.in_num);
      assert(ARRAY_SIZE(data.out_addr) >= data.out_num);




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