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DynamicLinking.md: add notes about memory/table exports #234

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DynamicLinking.md: add notes about memory/table exports #234

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DynamicLinking.md: add notes about memory/table exports
yamt Sep 3, 2024
7fd9b15
use backticks instead of quotes
yamt Sep 3, 2024
97a5e15
tweak a bit
yamt Sep 3, 2024
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19 changes: 19 additions & 0 deletions DynamicLinking.md
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Expand Up @@ -353,6 +353,25 @@ connect export the final relocated addresses (i.e. they cannot add
relocation; the loader, which knows `__memory_base`, can then calculate the
final relocated address.

### Note for memory/table exports

The commonly used C conventions including WASIp1 require modules to
export the `memory` memory and the `__indirect_function_table` table.

However, because PIE executables with this dynamic-linking convention
are already importing these instance resources, it's redundant to
export them as well. For that reason, for PIE executables, we don't
require these resources exported.
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Who is "we" here? If its WASI the perhaps this belongs in the wasi repo instead?

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i guess it should be in both. (wasi and here)

i added it here first because i feel the memory/table convention is more widely used than just wasi.


Shared libraries don't need to export these resources either.
They should also import these resources, since they share the memory
and function table with the main module. (The runtime linkers
can validate if it's actually the case and reject loading modules
otherwise.)

On the other hand, non-PIE executables need to export these instance
resources as usual.

## Implementation Status
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I wonder if we can/should add something under this header for wasi now?

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do you mean to update the implementation status section?


### LLVM Implementation
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