Re: [PATCH 3/3] lto-plugin: implement LDPT_GET_API_VERSION

[Alexander Monakov <amonakov@ispras.ru>]

On Mon, 11 Jul 2022, Martin Liška wrote:

> I've clarified that linker should return a value that is in range
> [minimal_api_supported, maximal_api_supported] and added an abort
> if it's not the case.

I noticed that we are placing a trap for C++ consumers such as mold
by passing min/max_api_supported as enum values. Unlike C, C++ disallows
out-of-range enum values, so when mold does

enum PluginLinkerAPIVersion {
  LAPI_V0 = 0,
  LAPI_V1,
};

get_api_version(const char *plugin_identifier,
                unsigned plugin_version,
                PluginLinkerAPIVersion minimal_api_supported,
                PluginLinkerAPIVersion maximal_api_supported,
                const char **linker_identifier,
                const char **linker_version) {

checks such as 'min_api_supported > LAPI_V1' can be optimized out. Also,
if a future tool passes LAPI_V2, it will trigger Clang's UBSan (GCC
-fsanitize-undefined=enum instruments loads but not retrieval of function
arguments).

I'd suggest to fix this on both sides by changing the arguments to plain
integer types.

Alexander