From bd6aab3513babbfd12abf5c7a5a2629e9cc6bb68 Mon Sep 17 00:00:00 2001
From: Coldwings <coldwings@me.com>
Date: Tue, 6 Feb 2024 14:35:24 +0800
Subject: [PATCH] fix UB that cause warning

---
 common/iovector.h | 33 +++++++++++++++++----------------
 1 file changed, 17 insertions(+), 16 deletions(-)

diff --git a/common/iovector.h b/common/iovector.h
index 08f6193f..53bc633f 100644
--- a/common/iovector.h
+++ b/common/iovector.h
@@ -34,6 +34,7 @@ limitations under the License.
 #include <cstring>
 #include <new>
 #include <memory>
+#include <array>
 #include <sys/uio.h>
 
 #include <photon/common/callback.h>
@@ -308,34 +309,34 @@ class iovector
     struct iovec* begin()
     {
         do_assert();
-        return iovs + iov_begin;
+        return iovs_ptr() + iov_begin;
     }
     const struct iovec* begin() const
     {
         do_assert();
-        return iovs + iov_begin;
+        return iovs_ptr() + iov_begin;
     }
     struct iovec* end()
     {
         do_assert();
-        return iovs + iov_end;
+        return iovs_ptr() + iov_end;
     }
     const struct iovec* end() const
     {
         do_assert();
-        return iovs + iov_end;
+        return iovs_ptr() + iov_end;
     }
     struct iovec& operator[] (int64_t i)
     {
         do_assert();
         assert(iov_begin + i < iov_end);
-        return iovs[iov_begin + i];
+        return iovs_ptr()[iov_begin + i];
     }
     const struct iovec& operator[] (int64_t i) const
     {
         do_assert();
         assert(iov_begin + i < iov_end);
-        return iovs[iov_begin + i];
+        return iovs_ptr()[iov_begin + i];
     }
 
     // push some stuff to the front, and
@@ -344,7 +345,7 @@ class iovector
     {
         do_assert();
         IF_ASSERT_RETURN(iov_begin > 0, 0);
-        iovs[--iov_begin] = iov;
+        iovs_ptr()[--iov_begin] = iov;
         return iov.iov_len;
     }
     size_t push_front(void* buf, size_t size)
@@ -369,7 +370,7 @@ class iovector
     {
         do_assert();
         IF_ASSERT_RETURN(iov_end < capacity, 0);
-        iovs[iov_end++] = iov;
+        iovs_ptr()[iov_end++] = iov;
         return iov.iov_len;
     }
     size_t push_back(void* buf, size_t size)
@@ -393,13 +394,13 @@ class iovector
     {
         do_assert();
         IF_ASSERT_RETURN(!empty(), 0);
-        return iovs[iov_begin++].iov_len;
+        return iovs_ptr()[iov_begin++].iov_len;
     }
     size_t pop_back()
     {
         do_assert();
         IF_ASSERT_RETURN(!empty(), 0);
-        return iovs[--iov_end].iov_len;
+        return iovs_ptr()[--iov_end].iov_len;
     }
 
     void clear()    // doesn't dispose()
@@ -772,7 +773,7 @@ class iovector
         clear_dispose();
         iov_end = end;
 
-        memcpy(begin(), rhs.begin(), iovcnt() * sizeof(iovs[0]));
+        memcpy(begin(), rhs.begin(), iovcnt() * sizeof(iovs_ptr()[0]));
         allocator()->copy(rhs.allocator(), rhs.nbases);
         nbases = rhs.nbases;
         rhs.nbases = 0;
@@ -791,7 +792,7 @@ class iovector
     }
 
     void update(iovector_view va) {
-        iov_begin = va.iov - iovs;
+        iov_begin = va.iov - iovs_ptr();
         iov_end = iov_begin + va.iovcnt;
     }
 
@@ -827,7 +828,7 @@ class iovector
     uint16_t capacity;              // total capacity
     uint16_t iov_begin, iov_end;    // [iov_begin, iov_end)
     uint16_t nbases;                // # of allocated pointers
-    struct iovec iovs[0];
+    // struct iovec iovs[];
 
     friend iovector* new_iovector(uint16_t capacity, uint16_t preserve);
     friend void delete_iovector(iovector* ptr);
@@ -841,7 +842,7 @@ class iovector
 
     inline __attribute__((always_inline))
     struct iovec* iovs_ptr() const {
-        return const_cast<struct iovec*>(iovs);
+        return reinterpret_cast<struct iovec*>(const_cast<iovector*>(this + 1));
     }
 
     // not allowed to freely construct / destruct
@@ -861,7 +862,7 @@ class iovector
 
     struct IOVAllocation_ : public IOAlloc
     {
-        void* bases[0];
+        void* bases[];
         void* do_allocate(int size, uint16_t& nbases, uint16_t capacity)
         {
             return do_allocate(size, size, nbases, capacity);
@@ -898,7 +899,7 @@ class iovector
 
     IOVAllocation_* allocator() const
     {   // this makes an assumption of the memory layout as `IOVectorEntity`
-        auto addr = (char*)this + sizeof(*this) +sizeof(iovs[0]) * capacity;
+        auto addr = (char*)this + sizeof(*this) +sizeof(iovs_ptr()[0]) * capacity;
         return (IOVAllocation_*)addr;
     }
     void dispose()