RFR: 8371048: ImageFileReader::open fails to check return value of osSupport::map_memory

[Alan Bateman]

On Tue, 11 Nov 2025 06:43:42 GMT, Jaikiran Pai <jpai at openjdk.org> wrote:

>> Check whether `osSupport::map_memory` actually succeeded in all compliation modes, instead of crashing shortly after in non-debug builds. Ideally we should fall back to just reading the entire file into memory manually or use seek+read, but this is good enough for now to avoid crashing.
>
> src/java.base/share/native/libjimage/imageFile.cpp line 334:
> 
>> 332:     // Memory map image (minimally the index.)
>> 333:     _index_data = (u1*)osSupport::map_memory(_fd, _name, 0, (size_t)map_size());
>> 334:     if (_index_data == nullptr) {
> 
> The rest of the code in the `libjimage` library uses `NULL`, including the return value in `osSupport::map_memory(...)`. So I think it would be better to use `NULL` here for consistency.

I agree, have a mix is annoying. In any case, changing the assert to have it fail looks right. The jimage file is opened during startup so less likely, but still possible, that this mmap fails.

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PR Review Comment: https://git.openjdk.org/jdk/pull/28087#discussion_r2521919635