From 955abfeeab624ade79d695440bb73ada8b073bfc Mon Sep 17 00:00:00 2001
From: conrad <conrad@localhost.localdomain>
Date: Wed, 5 Feb 2025 16:24:14 +1000
Subject: [PATCH] refactor to avoid using union

---
 include/armadillo_bits/arma_rng.hpp | 36 ++++++++++-------------------
 1 file changed, 12 insertions(+), 24 deletions(-)

diff --git a/include/armadillo_bits/arma_rng.hpp b/include/armadillo_bits/arma_rng.hpp
index 186dda68..21857f7c 100644
--- a/include/armadillo_bits/arma_rng.hpp
+++ b/include/armadillo_bits/arma_rng.hpp
@@ -267,22 +267,14 @@ arma_rng::set_seed_random()
     {
     try
       {
-      // TODO: replace union-based conversion with method based on std::memcpy() or C++20 bit_cast
-      
-      union
-        {
-        seed_type     a;
-        unsigned char b[sizeof(seed_type)];
-        } tmp;
-      
-      tmp.a = seed_type(0);
+      char tmp[sizeof(seed_type)] = {};
       
       std::ifstream f("/dev/urandom", std::ifstream::binary);
       
-      if(f.good())  { f.read((char*)(&(tmp.b[0])), sizeof(seed_type)); }
+      if(f.good())  { f.read(&(tmp[0]), sizeof(seed_type)); }
+      
+      if(f.good())  { std::memcpy(&seed2, &(tmp[0]), sizeof(seed_type)); }
       
-      if(f.good())  { seed2 = tmp.a; }
-        
       have_seed = (seed2 != seed_type(0));
       }
     catch(...) {}
@@ -299,21 +291,17 @@ arma_rng::set_seed_random()
     
     seed3 = static_cast<seed_type>( since_epoch_usec & 0xFFFF );
     
-    // TODO: replace union-based conversion with method based on std::memcpy() or C++20 bit_cast
+    unsigned char* a = (unsigned char*)std::malloc(std::size_t(4096));
     
-    union
+    unsigned char  b[sizeof(unsigned char*)] = {};
+    
+    if(a != nullptr)
       {
-      uword*        a;
-      unsigned char b[sizeof(uword*)];
-      } tmp;
-    
-    tmp.a = (uword*)malloc(sizeof(uword));
-    
-    if(tmp.a != nullptr)
-      {
-      for(size_t i=0; i<sizeof(uword*); ++i)  { seed4 += seed_type(tmp.b[i]); }
+      std::memcpy(&(b[0]), &a, sizeof(unsigned char*));
       
-      free(tmp.a);
+      for(size_t i=0; i<sizeof(unsigned char*); ++i)  { seed4 += seed_type(b[i]); }
+      
+      std::free(a);
       }
     }