Regression: MapCache type cache allocation skipped

[ploki]

Prerequisites

• I have written a descriptive issue title
• I have verified that I am using the latest version of ImageMagick
• I have searched open and closed issues to ensure it has not already been reported

Description

As a side effect, the changeset f39f646 made the MapCache allocation code unreachable. This issue also has the consequence of disabling multi-threading with OpenMP enabled algorithms because of the preliminary check on the type of cache of the images being manipulated.

Steps to Reproduce

Compile and run the following code using 6.9.9-27 (last good) and 6.9.9-28 (first bad)

#include <Magick++.h>
#include <iostream>

using namespace std;
using MagickCore::Quantum;

// test for the regression introduced along with f39f6469665edda3e43f05ba8ef2e9651222ddad
// $ g++ test.cpp -o test `pkg-config --libs --cflags Magick++` && ./test

void setConfiguration() {
  Magick::ResourceLimits::area(1024*1024);
  // small value to prevent the use of the MemoryCache
  Magick::ResourceLimits::memory(100);
  // Expects that images are allocated from the MapCache
  Magick::ResourceLimits::map(4*sizeof(QuantumRange)*1024*1024);
  Magick::ResourceLimits::disk(4*sizeof(QuantumRange)*1024*1024);
}
void printConfiguration() {
  cout << "Configuration:" << endl
       << "- Area: " << Magick::ResourceLimits::area() << endl
       << "- Memory: " << Magick::ResourceLimits::memory() << endl
       << "- Map: " << Magick::ResourceLimits::map() << endl
       << "- Disk: " << Magick::ResourceLimits::disk() << endl;
}

void printUsage(const char *when) {
  cout << "Usage " << when << ":" << endl
       << "- Area: " <<  MagickCore::GetMagickResource(MagickCore::AreaResource) << endl
       << "- Memory: " << MagickCore::GetMagickResource(MagickCore::MemoryResource) << endl
       << "- Map: " << MagickCore::GetMagickResource(MagickCore::MapResource) << endl
       << "- Disk: " << MagickCore::GetMagickResource(MagickCore::DiskResource) << endl;
}

int main(int argc, char **argv) {
  Magick::InitializeMagick(*argv);
  setConfiguration();
  printConfiguration();
  printUsage("before");
  Magick::Image image(Magick::Geometry(1000,1000), Magick::Color(0,0,0));
  printUsage("after");

  if (MagickCore::GetImagePixelCacheType(const_cast<Magick::Image&>(image).image())
      == MagickCore::MapCache) {
    cout << "Good! pixel cache type is MapCache" << endl;
    return 0;
  }
  cerr << "Not good! pixel cache is not MapCache" << endl;
  return 1;
}