Reject GCC asm memory operands on register variables (ImportC) - #5206
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Reject GCC asm memory operands on register variables (ImportC)#5206niy-ati wants to merge 4 commits into
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The frontend cannot diagnose m / =m constraints on register variables; reject them in GccAsmStatement_toIR when building indirect operands, matching C11 and GDC. Fixes ldc-developers#4967.
Do not fatal() after the first register+memory asm error so -verrors=0 can emit diagnostics for every illegal operand, matching GDC. Correct TEST_OUTPUT line numbers for the two asm statements.
kinke
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Jul 26, 2026
| } | ||
| if (registerMemError) | ||
| return; | ||
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This can be more easily integrated in the loop below, where we already check indirect operands for lvalue-ness (and where we shouldn't call fatal() either), inlining checkRegisterMemoryAsmOperand() (no need for an extra function for that).
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Other LDC-specific file additions to the DMD testsuite are named ldc_github_4967.c, to make clear that these are LDC-specific (incl. issue numbers).
Fold the ldc-developers#4967 check into the existing indirect-operand loop, drop the helper and fatal() on operand errors, and rename the fail_compilation test to ldc_github_4967.c.
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The other helper was fine, I just meant removing one of the two. And the check can be integrated more nicely, no need for |
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Summary
ImportC keeps
registerasSTCregister, but GCC style inline asm with"m"or"=m"constraints takes the operand address during LDC codegen. That is illegal C (same as GDC rejecting it) and was not caught in semantic analysis because the frontend does not interpret asm constraint strings.This rejects indirect memory asm operands that refer to a register variable in
GccAsmStatement_toIR, using the same diagnostic as other ImportC address of register cases.Fixes #4967.
Test plan
Added
tests/dmd/fail_compilation/issue4967.ccovering output and input"m"operands on aregister int.