fix Issue 18597 - more unsafe unaligned pointer errors

src/dmd/dstruct.d

@@ -479,6 +479,19 @@ extern (C++) class StructDeclaration : AggregateDeclaration
             Type origType = t;
             Type tb = t.toBasetype();
 
+            const hasPointers = tb.hasPointers();
+            if (hasPointers)
+            {
+                if ((stype.alignment() < Target.ptrsize ||
+                     (v.offset & (Target.ptrsize - 1))) &&
+                    sc.func.setUnsafe())
+                {
+                    .error(loc, "field `%s.%s` cannot assign to misaligned pointers in `@safe` code",
+                        toChars(), v.toChars());
+                    return false;
+                }
+            }
+
             /* Look for case of initializing a static array with a too-short
              * string literal, such as:
              *  char[5] foo = "abc";

src/dmd/initsem.d

@@ -33,6 +33,7 @@ import dmd.identifier;
 import dmd.init;
 import dmd.mtype;
 import dmd.statement;
+import dmd.target;
 import dmd.tokens;
 import dmd.visitor;
 
@@ -187,6 +188,17 @@ private extern(C++) final class InitializerSemanticVisitor : Visitor
                     errors = true;
                     continue;
                 }
+                if (vd.type.hasPointers)
+                {
+                    if ((t.alignment() < Target.ptrsize ||
+                         (vd.offset & (Target.ptrsize - 1))) &&
+                        sc.func.setUnsafe())
+                    {
+                        error(i.loc, "field `%s.%s` cannot assign to misaligned pointers in `@safe` code",
+                            sd.toChars(), vd.toChars());
+                        errors = true;
+                    }
+                }
                 for (size_t k = 0; k < nfields; k++)
                 {
                     VarDeclaration v2 = sd.fields[k];

test/fail_compilation/test18597.d

@@ -0,0 +1,27 @@
+/* TEST_OUTPUT:
+---
+fail_compilation/test18597.d(24): Error: field `Unaligned.p` cannot modify misaligned pointers in `@safe` code
+fail_compilation/test18597.d(25): Error: field `Unaligned.p` cannot assign to misaligned pointers in `@safe` code
+fail_compilation/test18597.d(26): Error: field `Unaligned.p` cannot assign to misaligned pointers in `@safe` code
+---
+*/
+
+// https://issues.dlang.org/show_bug.cgi?id=18597
+
+@safe:
+
+align(1)
+struct Unaligned
+{
+align(1):
+    ubyte filler;
+    int* p;
+}
+
+void test()
+{
+    Unaligned u;
+    u.p = new int;
+    Unaligned v = Unaligned(0, new int);
+    Unaligned w = { p : new int };
+}