Parsing very large C# files (>50MB) with Roslyn produces CompilationUnit with 0 members

Question

I'm trying to use Roslyn for modifying serializers code generated by svcutil.exe. basically, it contains several dozens medium classes, and two huge classes (reader and writer) that contains a function for every class in a very large schema, but nothing too crazy like very large strings or variable names. It works great for medium files (7MB), but when trying to parse a very large source file (50MB, ~600K lines), I'm getting an empty 'Members' collection for the CompilationUnitRoot. When turning on 'break on thrown exceptions' I see there's an InsufficientExecutionStackException thrown when loading the file. Is there any way around this?

When I inspect the CompilationUnitRoot, I see that FullSpan property is correctly set, but the Members, Attributes, and Usings collections are empty.

why don't split the file into smaller files? I guess it's auto-generated? Then simply modify the generator to emit Reader and Writer into separate files — phuclv
– phuclv, Commented Jan 16, 2023 at 15:19
I discovered that this was caused by a monstrous (11K lines) if/else statement, so that wouldn't help. — Omer Ran
– Omer Ran, Commented Jan 18, 2023 at 18:51
it should help if you break the body of the blocks into functions: if some_cond() return; else if (some_other_cond())... — phuclv
– phuclv, Commented Jan 19, 2023 at 0:35
There are many possible solutions, the trouble is I can't use Roslyn to make the transformation. — Omer Ran
– Omer Ran, Commented Jan 23, 2023 at 13:33

Omer Ran · Accepted Answer · 2023-01-18 18:57:25Z

0

I discovered that this was caused by some monstrous (11K lines) if/else statement, which are parsed in a recursion. Fortunately, these are all

if (...) return;
else if (...)

So I was able to pre-process the file and remove the 'else' keywords, breaking the recursion into to separate statements

edited Jan 18, 2023 at 18:57

answered Jan 18, 2023 at 18:53

Omer Ran

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