https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91292
--- Comment #7 from Richard Smith <richard-gccbugzilla at metafoo dot co.uk> --- (In reply to Patrick Palka from comment #3) > Hmm, but according to > http://itanium-cxx-abi.github.io/cxx-abi/abi.html#mangling.literal the > mangling of a negative integer literal is prefixed with "n", There is no such thing as a negative integer literal. The ABI document says "negative integer *values* are preceded with "n""; this case is reached when mangling fully-resolved template arguments via the <template-arg> ::= <expr-primary> production, not when mangling an instantiation-dependent expression. For example, given template<int> struct X {}; template<int N> void f(X<N * -1>, X<-1>) {} template void f<1>(X<-1>, X<-1>); the proper mangling is _Z1fILi1EEv1XIXmlT_ngLi1EEES0_ILin1EE using ngLi1E for the instantiation-dependent expression -1 and Lin1E for the non-instantiation-dependent value -1. (In reply to Patrick Palka from comment #4) > And if -(1) is to be mangled the same as -1, then shouldn't > > template<typename T> > typename std::enable_if<(int)sizeof(T) >= -(1), int>::type size1(T *t); > > template<typename T> > typename std::enable_if<(int)sizeof(T) >= -1, int>::type size1(T *t); > > be considered two declarations of the same function? But IIUC that would > contradict [temp.over.link]p5, which says > > Two expressions involving template parameters are considered equivalent if > two function definitions containing the expressions would satisfy the > one-definition rule > > but IIUC the one-definition rule fails here because -1 is not the same > (token-wise) as -(1). These declarations are functionally-equivalent but not equivalent, so a program is not permitted to contain both. That language rule exists in order to allow implementations to do things like ignore parentheses in mangling, as the Itanium C++ ABI does. Note that parentheses are never mangled (except for a weird corner case involving pointers to members), so if your argument were correct it would apply very broadly. For example, that argument would imply that -1 and (-1) would need different manglings.
