c++ - unsigned long long conflict with uint64_t? -

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• c++: long long int vs. long int vs. int64_t 3 answers

we use template specialization type parameter like

class my_template_class<uint64_t m>: public my_template_class_base<uint64_t> {  .... }  class my_template_class<unsigned long long,m>: public my_template_class_base<unsigned long long> {  .... } 

this working 64-bit compilation gcc. while when try 32 bit mode, reports "previous definition" above 2 classes.

so unsigned long long same uint64_t in 32-bit compilation not in 64-bit compliation?

the compilation difference cxx flag -m32 , -m64

so unsigned long long same uint64_t in 32-bit compilation not in 64-bit compilation?

yes.

in 32-bit mode, long 32 bits , long long 64 bits. in 64-bit mode, both 64 bits.

in 32-bit mode, compiler (more precisely <stdint.h> header) defines uint64_t unsigned long long, because unsigned long isn't wide enough.

in 64-bit mode, defines uint64_t unsigned long.

it could have defined unsigned long long in both modes. choice arbitrary; that's required has 64-bit type.

in general, each of integer types defined in <stdint.h> typedef predefined type appropriate characteristics. can't assume of them distinct predefined types.