Compiling problem when using API with newer g++ version

[p4p4]

My project that uses MiniSat did not compile anymore after
updating from Ubuntu 15.10 to 16.10
The following error message was shown:

/home/patrick/uni/SEA/libs/minisat/mtl/Map.h:32:99: error: missing template arguments before ‘(’ token
 late<class K> struct Hash  { uint32_t operator()(const K& k)               const { return hash(k);  } };
                                                                                               ^

and

/home/patrick/uni/SEA/libs/minisat/mtl/Map.h: In member function ‘uint32_t Minisat::DeepHash<K>::operator()(const K*) const’:
/home/patrick/uni/SEA/libs/minisat/mtl/Map.h:35:103: error: missing template arguments before ‘(’ token
 class K> struct DeepHash  { uint32_t operator()(const K* k)               const { return hash(*k);  } };

I could only fix it by replacing those lines as described in the following commit:
see changes
I applied the changes after i compiled MiniSAT, but before I compiled my own tool that includes "minisat/core/Solver.h". That way everything works again, but I'm not sure if that's really the way to resolve the problem..

I am using CMake to link everything together

SET_SOURCE_FILES_PROPERTIES(MiniSatApi.cpp PROPERTIES COMPILE_FLAGS "${COMPILE_FLAGS} -Wno-parentheses -D __STDC_LIMIT_MACROS -D __STDC_FORMAT_MACROS")

Before upgrading Ubuntu everything worked just fine.

g++ version:

$ g++ -v
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/6/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 6.2.0-5ubuntu12' --with-bugurl=file:///usr/share/doc/gcc-6/README.Bugs --enable-languages=c,ada,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-6 --program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-vtable-verify --enable-libmpx --enable-plugin --enable-default-pie --with-system-zlib --disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-6-amd64/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-6-amd64 --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-6-amd64 --with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --enable-objc-gc --enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 6.2.0 20161005 (Ubuntu 6.2.0-5ubuntu12) 

The same in Debian:
gcc version 6.1.1 20160802 (Debian 6.1.1-11)

However, if I switch to clang, everything works as usual.

Any ideas? Thank you in advance for your help!

[ShaswataJash]

If you analyze "mtl/Map.h" file in minisat, you can observe following lines at the very beginning of the header file -

template struct Hash { uint32_t operator()(const K& k) const { return hash(k); } };
template struct Equal { bool operator()(const K& k1, const K& k2) const { return k1 == k2; } };

template struct DeepHash { uint32_t operator()(const K* k) const { return hash(k); } };
template struct DeepEqual { bool operator()(const K k1, const K* k2) const { return *k1 == *k2; } };

static inline uint32_t hash(uint32_t x){ return x; }
static inline uint32_t hash(uint64_t x){ return (uint32_t)x; }
static inline uint32_t hash(int32_t x) { return (uint32_t)x; }
static inline uint32_t hash(int64_t x) { return (uint32_t)x; }

The root-cause is g++ is not able to see declaration of hash() functions used within a templatized struct Hash, Equal, DeepHash and DeepEqual. In the included header also, there is no declaration of hash() function - actually, the functions are defined/declared just after their usage location :) Needless to say, the solution is as simple as ensuring static inline definition of overloaded hash() functions are brought up before their usage so that -std=c++11 compilation is able to find the declaration of hash() function. Thus the solution would be to rearrange the above lines as follows -

static inline uint32_t hash(uint32_t x){ return x; }
static inline uint32_t hash(uint64_t x){ return (uint32_t)x; }
static inline uint32_t hash(int32_t x) { return (uint32_t)x; }
static inline uint32_t hash(int64_t x) { return (uint32_t)x; }

template struct Hash { uint32_t operator()(const K& k) const { return hash(k); } };
template struct Equal { bool operator()(const K& k1, const K& k2) const { return k1 == k2; } };

template struct DeepHash { uint32_t operator()(const K* k) const { return hash(k); } };
template struct DeepEqual { bool operator()(const K k1, const K* k2) const { return *k1 == *k2; } };