don't access empty vectors

Author: filikat

highs/ipm/hipo/factorhighs/CliqueStack.cpp

@@ -20,19 +20,23 @@ double* CliqueStack::setup(Int64 clique_size, bool& reallocation) {
   assert(!workspace_ && !worksize_);
   reallocation = false;
 
-  if (stack_.size() > 0) {
+  if (!stack_.empty()) {
     // This should not trigger reallocation, because the resize in init is done
     // with the maximum possible size of the stack.
     if (top_ + clique_size > stack_.size()) {
       reallocation = true;
       stack_.resize(top_ + clique_size, 0.0);
     }
 
-    workspace_ = &stack_[top_];
-    worksize_ = clique_size;
+    if (clique_size > 0) {
+      // accessing stack[top] is valid only if the clique is not empty,
+      // otherwise it may be out of bounds.
+      workspace_ = &stack_[top_];
+      worksize_ = clique_size;
 
-    // initialize workspace to zero
-    std::memset(workspace_, 0, worksize_ * sizeof(double));
+      // initialize workspace to zero
+      std::memset(workspace_, 0, worksize_ * sizeof(double));
+    }
   }
 
   return workspace_;
@@ -63,7 +67,7 @@ void CliqueStack::popChild() {
 void CliqueStack::pushWork(Int sn) {
   // Put the content of the workspace at the top of the stack
 
-  if (stack_.size() > 0) {
+  if (!stack_.empty()) {
     // stack_[top_] has lower address than workspace, so no need to resize.
     // workspace_ and stack_[top_] do not overlap, so use memcpy
     std::memcpy(&stack_[top_], workspace_, worksize_ * sizeof(double));

highs/ipm/hipo/factorhighs/HybridHybridFormatHandler.cpp

@@ -1,5 +1,6 @@
 #include "HybridHybridFormatHandler.h"
 
+#include <cassert>
 #include <cstring>
 
 #include "CallAndTimeBlas.h"
@@ -38,7 +39,11 @@ void HybridHybridFormatHandler::initFrontal() {
 
 void HybridHybridFormatHandler::initClique() {
   clique_.resize(S_->cliqueSize(sn_));
-  clique_ptr_ = clique_.data();
+
+  // If the clique size is zero, do not access the underlying pointer. This
+  // causes strange issues on windows. It's not a problem if clique_ptr_ remains
+  // null, because it will never be used in that case.
+  if (!clique_.empty()) clique_ptr_ = clique_.data();
 }
 
 void HybridHybridFormatHandler::assembleFrontal(Int i, Int j, double val) {
@@ -72,6 +77,9 @@ void HybridHybridFormatHandler::assembleFrontalMultiple(Int num,
 Int HybridHybridFormatHandler::denseFactorise(double reg_thresh) {
   Int status;
 
+  // either clique is valid, or clique is not needed
+  assert(clique_ptr_ || ldf_ == sn_size_);
+
   status = denseFactFP2FH(frontal_.data(), ldf_, sn_size_, nb_, data_);
   if (status) return status;