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Give a C struct with no data a placeholder member [patch] - #197
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ISO C forbids a struct with no members and MSVC rejects one, so an
empty class, or one holding only functions, came out as
typedef struct X { } X; and failed under -pedantic-errors. A
constructor on such a type also wrote {0} into a struct with no member
to zero. The C generator now writes one char member, with a note, when
a type has no fields, no base and no interfaces.
Fixes #181
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01X8BPy6trRZiUxiwJcbUGzR
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Fixes #181
What changed
CGenerator.GenerateClassDeclarationalways wrote the struct body, even when nothing went into it. That happens for an emptyClassDeclarationand for a class whose members are all functions. Both came out astypedef struct X { } X;. ISO C forbids a struct with no members, so this fails under-pedantic-errors, and MSVC rejects it outright with C2016. A constructor on such a type also wroteSelf self = {0};, and gcc reportsexcess elements in struct initializerbecause there is no member for the0to initialise.The issue offered two options. This takes the first one: a type with no fields, no base and no interfaces now gets one
char unused_;member, with a note before it. It keeps a single rule for every type. The constructor's{0}and theType_create()call sites stay valid without any changes. A type with a base or interfaces is not affected, because its embedded member is already the first member.Tests
CGeneratorTests.Struct_WithNoData_GetsAPlaceholderMember:char unused_;.CGeneratedSourceCompilesTests.TypesWithNoData_CompileAsStrictC: this is the case the acceptance criteria ask for. It generates a header with an empty class that has a constructor, and a static-onlyMathX. It compiles the header and a driver that calls both under-std=c11 -pedantic-errors.With the generator change reverted, both tests fail. gcc reports
struct has no memberstwice andexcess elements in struct initializeronce. With the change, the full suite passes (1102/1102).The existing exemplar compile still uses
-pedantic. I left it alone so the scope matches the issue.🤖 Generated with Claude Code
https://claude.ai/code/session_01X8BPy6trRZiUxiwJcbUGzR
Generated by Claude Code