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book/duplicates.md: discriminator -> disambiguator #513

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Jun 20, 2021
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book/duplicates.md: discriminator -> disambiguator #513

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10 changes: 5 additions & 5 deletions book/src/duplicates.md
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Original file line number Diff line number Diff line change
Expand Up @@ -42,14 +42,14 @@ static SYM: u8 = 0;

which results in a collision.

To avoid this issue we store each interned string as a JSON object with 3 fields: the message itself, the name of the crate that invoked the macro, and a 64-bit integer "discriminator".
The discriminator is a hash of the source code location of the log statement so it should be unique per crate.
To avoid this issue we store each interned string as a JSON object with 3 fields: the message itself, the name of the crate that invoked the macro, and a 64-bit integer "disambiguator".
The disambiguator is a hash of the source code location of the log statement so it should be unique per crate.
Now these two macro invocations will produce something like this:

``` rust,no_run,noplayground
// first info! invocation
{
#[export_name = "{ \"package\": \"my-app\", \"data\": \".. DONE\", \"discriminator\": \"1379186119\" }"]
#[export_name = "{ \"package\": \"my-app\", \"data\": \".. DONE\", \"disambiguator\": \"1379186119\" }"]
#[link_section = ".."]
static SYM: u8 = 0;
}
Expand All @@ -58,13 +58,13 @@ Now these two macro invocations will produce something like this:

// second info! invocation
{
#[export_name = "{ \"package\": \"my-app\", \"data\": \".. DONE\", \"discriminator\": \"346188945\" }"]
#[export_name = "{ \"package\": \"my-app\", \"data\": \".. DONE\", \"disambiguator\": \"346188945\" }"]
#[link_section = ".."]
static SYM: u8 = 0;
}
```

These symbols do not collide because their discriminator fields are different so the program will link correctly.
These symbols do not collide because their disambiguator fields are different so the program will link correctly.

Because duplicate strings are kept in the final binary this linker-based interner is not really an interner.
A proper interner returns the same index when the same string is interned several times.
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