How to test if a string is pointing into read-only memory?

Elronnd elronnd at
Tue Oct 12 09:20:42 UTC 2021

On Tuesday, 12 October 2021 at 08:19:01 UTC, jfondren wrote:
> What's a reliable test that could be used in a toStringz that 
> skips allocation when given a string in read-only memory?

There is no good way.

- You could peek in /proc, but that's not portable

- You could poke the data and catch the resulting fault; but 
that's: 1) horrible, 2) slow, 3) problematic wrt threading, 4) 
sensitive to user code mapping its own memory and then remapping 
as rw (or unmapping)

- You could make a global hash table into which are registered 
the addresses of all rodata; but that is difficult to get right 
across translation units, especially in the face of dynamic 
linking.  This is probably the most feasible, but is really not 
worth the hassle.

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