pull failed-unwind-step register-block-restore out of each impl, just do it on the caller side; pull out module-less read-the-stack-pointer unwind fallback from pe/x64 unwinder, use in module-less unwinds in all cases; call into from pe/x64 unwinder in fallback case

src/unwind/unwind.c

@@ -6,6 +6,41 @@
 
 #include "unwind/generated/unwind.meta.c"
 
+////////////////////////////////
+//~ rjf: Moduleless Unwinder
+
+internal UWND_StepResult
+uwnd_step_moduleless(Arch arch, MemoryMap *memory_map, void *regs)
+{
+  UWND_StepResult result = {UWND_StepStatus_Error};
+  {
+    B32 done = 0;
+    ARCH_Info *arch_info = arch_info_from_arch(arch);
+    U64 addr_size = byte_size_from_arch(arch);
+    
+    // rjf: read new ip from stack pointer
+    U64 sp = arch_sp_from_reg_block(arch_info, regs);
+    U64 new_ip = 0;
+    Rng1U64 new_ip_vaddr_range = r1u64(sp, sp+addr_size);
+    if(memory_map_read(memory_map, new_ip_vaddr_range, &new_ip) != addr_size)
+    {
+      done = 1;
+      result.status = UWND_StepStatus_FailedMemoryRead;
+      result.missed_read_vaddr_range = new_ip_vaddr_range;
+    }
+    
+    // rjf: commit
+    if(!done)
+    {
+      U64 new_sp = sp+addr_size;
+      arch_reg_block_write_ip(arch_info, regs, new_ip);
+      arch_reg_block_write_sp(arch_info, regs, new_sp);
+      result.status = UWND_StepStatus_Good;
+    }
+  }
+  return result;
+}
+
 ////////////////////////////////
 //~ rjf: Abstracted Unwind Step Functions
 
@@ -15,7 +50,7 @@ uwnd_step(UWND_Unwinder unwinder, Arch arch, MemoryMap *memory_map, UWND_ModuleI
   UWND_StepResult result = {UWND_StepStatus_Error};
   switch(unwinder)
   {
-    default:{}break;
+    default:{result = uwnd_step_moduleless(arch, memory_map, regs);}break;
 #define X(name, namespace_lower) case UWND_Unwinder_##name:{result = namespace_lower##_uwnd_step(arch, memory_map, module_info, tls_vaddr, regs, cfa_out);}break;
     UWND_Unwinder_XList
 #undef X

src/unwind/unwind.h

@@ -37,6 +37,11 @@ struct UWND_ModuleInfo
   void *unwind_info;
 };
 
+////////////////////////////////
+//~ rjf: Moduleless Unwinder
+
+internal UWND_StepResult uwnd_step_moduleless(Arch arch, MemoryMap *memory_map, void *regs);
+
 ////////////////////////////////
 //~ rjf: Abstracted Unwind Step Functions