Shorten symbols by truncating the hash.

[eddyb]

No description provided.

[alexcrichton]

I may have missed the conversion, but why use base64 over hex? 64bits == 16 characters which doesn't seem that large (it's how big all the hashes used to be anyway).

[eddyb]

The symbol length has been reduced and the hash is easier to ignore:

> nm --defined-only ./x*/stage1/lib/r*/x*/l*/libstd-*.so | grep -v 'expr_fn\|\.\.\|GCC' | c++filt | sort -R | head
0000000000109ac0 T fmt::rt::Piece::Piece::Argument::hqMrQ_xr.r5s$::v0.9.pre
0000000000121a14 R libc::consts::os::posix88::EKEYREJECTED::h.vIV0_KaexA$aE::v0.9.pre
00000000000863f0 T i32::Add$i32::add::h8W3PoE86stU$43aR::v0.9.pre
0000000000078520 T rt::global_heap::exchange_free_::hyPa8N3dH0UY$aZ::v0.9.pre
000000000008dba0 T u32::Default$u32::default::hITfgkj1OV_c$kOar::v0.9.pre
00000000000b0e10 T num::FromPrimitive$uint::from_uint::hZzVzAOkD6_w$JVa0::v0.9.pre
0000000000092390 T f32::Real$f32::ln_2::hcJ17WXwyr0E$BJaX::v0.9.pre
000000000008c230 T u16::CheckedDiv$u16::checked_div::htJ2QjTyy09I$jYaa::v0.9.pre
00000000000b0e90 T num::FromPrimitive$uint::from_u16::hKTglBKguS2A$JVa2::v0.9.pre
0000000000078600 t u32::glue_take::hRNP0EbNP9Rk$az

I'm considering rewriting back::link::sanitize to output C++ mangling-like encodings, to make symbols like these nicer:

_$LP$option..Option$LT$io..pipe..PipeStream$GT$$C$comm..SharedChan$LT$$LP$int$C$$UP$$x5bu8$x5d$RP$$GT$$RP$::glue_visit::ha2rl8hnzh3E$aY
sync..arc..ArcData$LT$sync..mpsc_queue..State$LT$$LP$int$C$$UP$$x5bu8$x5d$RP$$C$comm..Packet$GT$$GT$::glue_visit::hWLcjb4N7zVk$ab
_$UP$$SP$condition..Handler$LT$io..IoError$C$$LP$$RP$$GT$::glue_free::hszG7fICVwzI$ab

Though it will be hard without having the original (nested) type information (sanitize just gets a string now).

[eddyb]

@alexcrichton It's not that bad with hex instead of base64, it seems (though you can tell the difference):

> nm --defined-only ./x*/stage1/lib/r*/x*/l*/libstd-*.so | grep -v 'expr_fn\|\.\.\|GCC\|str\|vtable' | c++filt | sort -R | head
0000000000098880 T f64::log2::h538bc4f03a4e4f8daM::v0.9.pre
0000000000111d60 T repr::Repr$int::write_repr::hffda9a03775c36faBsad::v0.9.pre
00000000000ffec0 t io::Reader::bytes::h96688705a1fe48ecam::v0.9.pre
0000000000124acc R libc::consts::os::sysconf::_SC_SYNCHRONIZED_IO::h757c915c4e1bfec5aI::v0.9.pre
00000000000b4b40 T num::FromPrimitive$u64::from_f32::hbebb3eb62bb65c6cMlaQ::v0.9.pre
00000000000b5ad0 T to_bytes::IterBytes$f32::iter_bytes::hdc01dc1017ca4c92P2ax::v0.9.pre
0000000000099b90 T f64::Exponential$f64::exp2::h165ce8970a5024afL4ay::v0.9.pre
0000000000093b70 T f32::atan::h835d81dcdb9e8aecaD::v0.9.pre
0000000000124ad8 R libc::consts::os::sysconf::_SC_MEMLOCK::h757c915c4e1bfec5aU::v0.9.pre
0000000000125cb0 R io::GroupWrite::hb29fe352308d0a41aF::v0.9.pre