On Monday, 23 May 2016 at 20:34:19 UTC, Walter Bright wrote:
On 5/23/2016 12:32 PM, Timon Gehr wrote:
Isn't it enough to create
references to previously embedded mangled symbols (i-th symbol
already mangled)
while generating the mangled string?
That's been covered upthread, and VC++/g++ do that. But as
shown, it is inadequate. There's a lot more redundancy than
just the identifiers.
Yes, not all redundancy is covered. However, I think all
non-pathologic blow-ups are avoided.
Let's look at the properties of the Itanium C++ ABI mangling:
1. Guaranteed linear size name for recursive types that have
exponential size names.
2. Compression speed can be linear to the size of the compressed
name (i.e. no need to create an exponential garbage name just to
compress it).
3. Decompression easy, possible without tools and speed linear to
size of the compressed name.
4. Name retains some redundancy (in itself and when compared to
other mangled names), well suited for a follow-up compression.
Compare this to apply some arbitrary compression algorithm to a
name of exponential size:
1. Exponential size names remain exponential size. Yes, up until
the view size, some compression algorithms guarantee that, but
they can not guarantee it in the general case.
2. Compression needs the whole name first.
3. Decompression only possible with tools.
4. Multiple mangled names can not be compressed well.
