Fix for not applying debug margin in Generic algorithm.

Ported test for linear algorithm from VMA.

Code by @medranSolus

.gitignore

@@ -1 +1,2 @@
 build/
+bin/

src/Common.h

@@ -349,6 +349,8 @@ struct MyUniformRandomNumberGenerator
 {
     typedef uint32_t result_type;
     MyUniformRandomNumberGenerator(RandomNumberGenerator& gen) : m_Gen(gen) { }
+    static uint32_t min() { return 0; }
+    static uint32_t max() { return UINT32_MAX; }
     uint32_t operator()() { return m_Gen.Generate(); }
 
 private:

src/D3D12MemAlloc.cpp

@@ -4009,8 +4009,8 @@ bool BlockMetadata_Generic::CheckAllocation(
         return false;
     }
 
-    // Start from offset equal to beginning of this suballocation.
-    UINT64 offset = suballoc.offset;
+    // Start from offset equal to beginning of this suballocation and debug margin of previous allocation if present.
+    UINT64 offset = suballoc.offset + (suballocItem == m_Suballocations.cbegin() ? 0 : GetDebugMargin());
 
     // Apply alignment.
     offset = AlignUp(offset, allocAlignment);
@@ -4018,7 +4018,7 @@ bool BlockMetadata_Generic::CheckAllocation(
     // Calculate padding at the beginning based on current offset.
     const UINT64 paddingBegin = offset - suballoc.offset;
 
-    // Fail if requested size plus margin before and after is bigger than size of this suballocation.
+    // Fail if requested size plus margin after is bigger than size of this suballocation.
     if(paddingBegin + allocSize + GetDebugMargin() > suballoc.size)
     {
         return false;

src/D3D12Sample.cpp

@@ -20,8 +20,8 @@
 // THE SOFTWARE.
 //
 
-#include "D3D12MemAlloc.h"
 #include "Common.h"
+#include "D3D12MemAlloc.h"
 #include "Tests.h"
 #include <atomic>
 #include <Shlwapi.h> // For StrStrI