nbtheory.cpp: warning: possibly dangling reference to a temporary

[vgfl]

Hello there,

A small warning with that file with g++-13.1. Just in the unlikely case it points at something serious:

/usr/local/gcc-13.1/bin/g++-13.1 -g2 -pipe -std=c++20 -pedantic -Wall -DNDEBUG -O3 -fPIC -fvisibility=hidden -fvisibility-inlines-hidden -pthread -c nbtheory.cpp
nbtheory.cpp: In function ‘const CryptoPP::word16* CryptoPP::GetPrimeTable(unsigned int&)’:
nbtheory.cpp:55:36: warning: possibly dangling reference to a temporary [-Wdangling-reference]
   55 |         const std::vector<word16> &primeTable = Singleton<std::vector<word16>, NewPrimeTable>().Ref();
      |                                    ^~~~~~~~~~
nbtheory.cpp:55:100: note: the temporary was destroyed at the end of the full expression ‘CryptoPP::Singleton<std::vector<short unsigned int>, CryptoPP::NewPrimeTable>((CryptoPP::NewPrimeTable(), CryptoPP::NewPrimeTable())).CryptoPP::Singleton<std::vector<short unsigned int>, CryptoPP::NewPrimeTable>::Ref()’
   55 |         const std::vector<word16> &primeTable = Singleton<std::vector<word16>, NewPrimeTable>().Ref();
      |                                                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~

Thanks!

[noloader]

Thanks @vgfl,

Yeah, I am seeing that too with -Wdangling-reference. I'll take a look at it soon.

At first glance, I think the prime table is being built on the fly. I think we should just precompute it, and put it in a rodata section. The OS can load it into memory if needed, and discard it when not needed.

Once the table is precomputed, we can do away with the Singleton to build it on the fly.

[noloader]

Ok, this should be cleared at Commit 6ecc789df1ce.