Compilation fails in release mode

[wonder-sk]

When I set CMAKE_BUILD_TYPE to Release then I get compilation errors due to warnings being handled as errors (-Werror compilation flag). With CMAKE_BUILD_TYPE=Debug, there are no warnings/errors.

This is with GCC 9.3.0 on ubuntu 20.04.

$ ninja      
[0/1] Re-running CMake...
-- Configuring done
-- Generating done
-- Build files have been written to: /home/martin/inst/untwine/build-ubuntu
[1/16] Building CXX object CMakeFiles/untwine.dir/epf/Grid.cpp.o
FAILED: CMakeFiles/untwine.dir/epf/Grid.cpp.o 
/usr/bin/c++   -Iinclude -isystem /usr/include/gdal -O3 -DNDEBUG   -Wno-implicit-fallthrough -Wno-int-in-bool-context -Wno-dangling-else -Wno-noexcept-type -Wall -Wextra -Wpointer-arith -Wcast-align -Wcast-qual -Wno-error=parentheses -Wno-error=cast-qual -Wredundant-decls -Wno-unused-parameter -Wno-unused-variable -Wno-long-long -Wno-unknown-pragmas -Wno-deprecated-declarations -Werror -std=gnu++11 -MD -MT CMakeFiles/untwine.dir/epf/Grid.cpp.o -MF CMakeFiles/untwine.dir/epf/Grid.cpp.o.d -o CMakeFiles/untwine.dir/epf/Grid.cpp.o -c ../epf/Grid.cpp
In file included from ../epf/EpfTypes.hpp:25,
                 from ../epf/Epf.hpp:21,
                 from ../epf/Grid.cpp:17:
../epf/../untwine/FileDimInfo.hpp: In function ‘std::istream& untwine::operator>>(std::istream&, untwine::FileDimInfo&)’:
../epf/../untwine/FileDimInfo.hpp:43:33: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
   43 |     in >> fdi.name >> (int&)fdi.type >> fdi.offset;
      |                             ~~~~^~~~
cc1plus: all warnings being treated as errors
[3/16] Building CXX object CMakeFiles/untwine.dir/epf/BufferCache.cpp.o
FAILED: CMakeFiles/untwine.dir/epf/BufferCache.cpp.o 
/usr/bin/c++   -Iinclude -isystem /usr/include/gdal -O3 -DNDEBUG   -Wno-implicit-fallthrough -Wno-int-in-bool-context -Wno-dangling-else -Wno-noexcept-type -Wall -Wextra -Wpointer-arith -Wcast-align -Wcast-qual -Wno-error=parentheses -Wno-error=cast-qual -Wredundant-decls -Wno-unused-parameter -Wno-unused-variable -Wno-long-long -Wno-unknown-pragmas -Wno-deprecated-declarations -Werror -std=gnu++11 -MD -MT CMakeFiles/untwine.dir/epf/BufferCache.cpp.o -MF CMakeFiles/untwine.dir/epf/BufferCache.cpp.o.d -o CMakeFiles/untwine.dir/epf/BufferCache.cpp.o -c ../epf/BufferCache.cpp
In file included from ../epf/EpfTypes.hpp:25,
                 from ../epf/BufferCache.hpp:20,
                 from ../epf/BufferCache.cpp:16:
../epf/../untwine/FileDimInfo.hpp: In function ‘std::istream& untwine::operator>>(std::istream&, untwine::FileDimInfo&)’:
../epf/../untwine/FileDimInfo.hpp:43:33: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
   43 |     in >> fdi.name >> (int&)fdi.type >> fdi.offset;
      |                             ~~~~^~~~
cc1plus: all warnings being treated as errors
[4/16] Building CXX object CMakeFiles/untwine.dir/epf/Reprocessor.cpp.o
FAILED: CMakeFiles/untwine.dir/epf/Reprocessor.cpp.o 
/usr/bin/c++   -Iinclude -isystem /usr/include/gdal -O3 -DNDEBUG   -Wno-implicit-fallthrough -Wno-int-in-bool-context -Wno-dangling-else -Wno-noexcept-type -Wall -Wextra -Wpointer-arith -Wcast-align -Wcast-qual -Wno-error=parentheses -Wno-error=cast-qual -Wredundant-decls -Wno-unused-parameter -Wno-unused-variable -Wno-long-long -Wno-unknown-pragmas -Wno-deprecated-declarations -Werror -std=gnu++11 -MD -MT CMakeFiles/untwine.dir/epf/Reprocessor.cpp.o -MF CMakeFiles/untwine.dir/epf/Reprocessor.cpp.o.d -o CMakeFiles/untwine.dir/epf/Reprocessor.cpp.o -c ../epf/Reprocessor.cpp
In file included from ../epf/EpfTypes.hpp:25,
                 from ../epf/Reprocessor.hpp:16,
                 from ../epf/Reprocessor.cpp:16:
../epf/../untwine/FileDimInfo.hpp: In function ‘std::istream& untwine::operator>>(std::istream&, untwine::FileDimInfo&)’:
../epf/../untwine/FileDimInfo.hpp:43:33: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
   43 |     in >> fdi.name >> (int&)fdi.type >> fdi.offset;
      |                             ~~~~^~~~
cc1plus: all warnings being treated as errors
[5/16] Building CXX object CMakeFiles/untwine.dir/epf/Cell.cpp.o
FAILED: CMakeFiles/untwine.dir/epf/Cell.cpp.o 
/usr/bin/c++   -Iinclude -isystem /usr/include/gdal -O3 -DNDEBUG   -Wno-implicit-fallthrough -Wno-int-in-bool-context -Wno-dangling-else -Wno-noexcept-type -Wall -Wextra -Wpointer-arith -Wcast-align -Wcast-qual -Wno-error=parentheses -Wno-error=cast-qual -Wredundant-decls -Wno-unused-parameter -Wno-unused-variable -Wno-long-long -Wno-unknown-pragmas -Wno-deprecated-declarations -Werror -std=gnu++11 -MD -MT CMakeFiles/untwine.dir/epf/Cell.cpp.o -MF CMakeFiles/untwine.dir/epf/Cell.cpp.o.d -o CMakeFiles/untwine.dir/epf/Cell.cpp.o -c ../epf/Cell.cpp
In file included from ../epf/EpfTypes.hpp:25,
                 from ../epf/Cell.hpp:22,
                 from ../epf/Cell.cpp:14:
../epf/../untwine/FileDimInfo.hpp: In function ‘std::istream& untwine::operator>>(std::istream&, untwine::FileDimInfo&)’:
../epf/../untwine/FileDimInfo.hpp:43:33: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
   43 |     in >> fdi.name >> (int&)fdi.type >> fdi.offset;
      |                             ~~~~^~~~
cc1plus: all warnings being treated as errors
[6/16] Building CXX object CMakeFiles/untwine.dir/epf/Writer.cpp.o
FAILED: CMakeFiles/untwine.dir/epf/Writer.cpp.o 
/usr/bin/c++   -Iinclude -isystem /usr/include/gdal -O3 -DNDEBUG   -Wno-implicit-fallthrough -Wno-int-in-bool-context -Wno-dangling-else -Wno-noexcept-type -Wall -Wextra -Wpointer-arith -Wcast-align -Wcast-qual -Wno-error=parentheses -Wno-error=cast-qual -Wredundant-decls -Wno-unused-parameter -Wno-unused-variable -Wno-long-long -Wno-unknown-pragmas -Wno-deprecated-declarations -Werror -std=gnu++11 -MD -MT CMakeFiles/untwine.dir/epf/Writer.cpp.o -MF CMakeFiles/untwine.dir/epf/Writer.cpp.o.d -o CMakeFiles/untwine.dir/epf/Writer.cpp.o -c ../epf/Writer.cpp
In file included from ../epf/EpfTypes.hpp:25,
                 from ../epf/Writer.hpp:21,
                 from ../epf/Writer.cpp:18:
../epf/../untwine/FileDimInfo.hpp: In function ‘std::istream& untwine::operator>>(std::istream&, untwine::FileDimInfo&)’:
../epf/../untwine/FileDimInfo.hpp:43:33: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
   43 |     in >> fdi.name >> (int&)fdi.type >> fdi.offset;
      |                             ~~~~^~~~
cc1plus: all warnings being treated as errors
[7/16] Building CXX object CMakeFiles/untwine.dir/epf/FileProcessor.cpp.o
FAILED: CMakeFiles/untwine.dir/epf/FileProcessor.cpp.o 
/usr/bin/c++   -Iinclude -isystem /usr/include/gdal -O3 -DNDEBUG   -Wno-implicit-fallthrough -Wno-int-in-bool-context -Wno-dangling-else -Wno-noexcept-type -Wall -Wextra -Wpointer-arith -Wcast-align -Wcast-qual -Wno-error=parentheses -Wno-error=cast-qual -Wredundant-decls -Wno-unused-parameter -Wno-unused-variable -Wno-long-long -Wno-unknown-pragmas -Wno-deprecated-declarations -Werror -std=gnu++11 -MD -MT CMakeFiles/untwine.dir/epf/FileProcessor.cpp.o -MF CMakeFiles/untwine.dir/epf/FileProcessor.cpp.o.d -o CMakeFiles/untwine.dir/epf/FileProcessor.cpp.o -c ../epf/FileProcessor.cpp
In file included from ../epf/EpfTypes.hpp:25,
                 from ../epf/FileProcessor.hpp:14,
                 from ../epf/FileProcessor.cpp:14:
../epf/../untwine/FileDimInfo.hpp: In function ‘std::istream& untwine::operator>>(std::istream&, untwine::FileDimInfo&)’:
../epf/../untwine/FileDimInfo.hpp:43:33: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
   43 |     in >> fdi.name >> (int&)fdi.type >> fdi.offset;
      |                             ~~~~^~~~
cc1plus: all warnings being treated as errors
[8/16] Building CXX object CMakeFiles/untwine.dir/bu/PyramidManager.cpp.o
FAILED: CMakeFiles/untwine.dir/bu/PyramidManager.cpp.o 
/usr/bin/c++   -Iinclude -isystem /usr/include/gdal -O3 -DNDEBUG   -Wno-implicit-fallthrough -Wno-int-in-bool-context -Wno-dangling-else -Wno-noexcept-type -Wall -Wextra -Wpointer-arith -Wcast-align -Wcast-qual -Wno-error=parentheses -Wno-error=cast-qual -Wredundant-decls -Wno-unused-parameter -Wno-unused-variable -Wno-long-long -Wno-unknown-pragmas -Wno-deprecated-declarations -Werror -std=gnu++11 -MD -MT CMakeFiles/untwine.dir/bu/PyramidManager.cpp.o -MF CMakeFiles/untwine.dir/bu/PyramidManager.cpp.o.d -o CMakeFiles/untwine.dir/bu/PyramidManager.cpp.o -c ../bu/PyramidManager.cpp
In file included from ../bu/BuTypes.hpp:21,
                 from ../bu/Processor.hpp:18,
                 from ../bu/PyramidManager.cpp:22:
../bu/../untwine/FileDimInfo.hpp: In function ‘std::istream& untwine::operator>>(std::istream&, untwine::FileDimInfo&)’:
../bu/../untwine/FileDimInfo.hpp:43:33: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
   43 |     in >> fdi.name >> (int&)fdi.type >> fdi.offset;
      |                             ~~~~^~~~
cc1plus: all warnings being treated as errors
[9/16] Building CXX object CMakeFiles/untwine.dir/bu/Processor.cpp.o
FAILED: CMakeFiles/untwine.dir/bu/Processor.cpp.o 
/usr/bin/c++   -Iinclude -isystem /usr/include/gdal -O3 -DNDEBUG   -Wno-implicit-fallthrough -Wno-int-in-bool-context -Wno-dangling-else -Wno-noexcept-type -Wall -Wextra -Wpointer-arith -Wcast-align -Wcast-qual -Wno-error=parentheses -Wno-error=cast-qual -Wredundant-decls -Wno-unused-parameter -Wno-unused-variable -Wno-long-long -Wno-unknown-pragmas -Wno-deprecated-declarations -Werror -std=gnu++11 -MD -MT CMakeFiles/untwine.dir/bu/Processor.cpp.o -MF CMakeFiles/untwine.dir/bu/Processor.cpp.o.d -o CMakeFiles/untwine.dir/bu/Processor.cpp.o -c ../bu/Processor.cpp
In file included from ../bu/BuTypes.hpp:21,
                 from ../bu/Processor.hpp:18,
                 from ../bu/Processor.cpp:22:
../bu/../untwine/FileDimInfo.hpp: In function ‘std::istream& untwine::operator>>(std::istream&, untwine::FileDimInfo&)’:
../bu/../untwine/FileDimInfo.hpp:43:33: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
   43 |     in >> fdi.name >> (int&)fdi.type >> fdi.offset;
      |                             ~~~~^~~~
cc1plus: all warnings being treated as errors
[10/16] Building CXX object CMakeFiles/untwine.dir/epf/Epf.cpp.o
FAILED: CMakeFiles/untwine.dir/epf/Epf.cpp.o 
/usr/bin/c++   -Iinclude -isystem /usr/include/gdal -O3 -DNDEBUG   -Wno-implicit-fallthrough -Wno-int-in-bool-context -Wno-dangling-else -Wno-noexcept-type -Wall -Wextra -Wpointer-arith -Wcast-align -Wcast-qual -Wno-error=parentheses -Wno-error=cast-qual -Wredundant-decls -Wno-unused-parameter -Wno-unused-variable -Wno-long-long -Wno-unknown-pragmas -Wno-deprecated-declarations -Werror -std=gnu++11 -MD -MT CMakeFiles/untwine.dir/epf/Epf.cpp.o -MF CMakeFiles/untwine.dir/epf/Epf.cpp.o.d -o CMakeFiles/untwine.dir/epf/Epf.cpp.o -c ../epf/Epf.cpp
In file included from ../epf/EpfTypes.hpp:25,
                 from ../epf/Epf.hpp:21,
                 from ../epf/Epf.cpp:14:
../epf/../untwine/FileDimInfo.hpp: In function ‘std::istream& untwine::operator>>(std::istream&, untwine::FileDimInfo&)’:
../epf/../untwine/FileDimInfo.hpp:43:33: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
   43 |     in >> fdi.name >> (int&)fdi.type >> fdi.offset;
      |                             ~~~~^~~~
cc1plus: all warnings being treated as errors
ninja: build stopped: subcommand failed.

[abellgithub]

Heh. I was surprised that the compiler let me do this originally, but I was lazy.

[abellgithub]

Fixed with 154e7f7