erts: Fix undefined behavior of driver start callback - #11435
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It's UB in C to call functions with too many arguments. User drivers expect two arguments to start() callback. Only call system drivers with the extra third argument.
It's unusable for user drivers.
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Pull request overview
This PR fixes undefined behavior in ERTS by ensuring the port driver start callback is invoked with the correct argument count: two arguments for normal/user drivers, and three arguments (including SysDriverOpts*) only for system drivers.
Changes:
- Split driver start callbacks into
start(2 args) andstart_sys_drv(3 args) and call the appropriate one fromerts_open_driver(). - Extend internal driver initialization to classify system drivers and wire up the correct callback pointer.
- Update driver entry documentation, but it currently drops important details about
starterror return conventions.
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| erts/emulator/beam/io.c | Calls user-driver start with 2 args; calls system-driver start_sys_drv with SysDriverOpts*; updates driver initialization to set the right pointer. |
| erts/emulator/beam/global.h | Adjusts internal erts_driver_t_ to store separate start vs start_sys_drv function pointers. |
| erts/doc/references/driver_entry.md | Updates the documented ErlDrvEntry.start signature, but currently omits documented error return conventions. |
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Fix #11385
It's UB in C to call functions with too many arguments.
User drivers expect two arguments to
startcallback. Only call system drivers with the extra third argument.