Neither fixpoint exercises the in-process internal assembler (--assembler
internal): fixpoint.sh assembles via qbe+gcc, fixpoint-native.sh assembles
the native .s with gcc. A miscompilation that only corrupts the internal
assembler's object output therefore passes both fixpoints cleanly — which is
exactly how the sret-Result field-read bug (fixed in the previous commit)
escaped the fixpoint gate.
scripts/fixpoint-native-internal.sh closes that gap. It compiles a small
representative program (record-returning function with sret-Result field
reads, plus immutable string literals) with BOTH --assembler internal and
--assembler external, then asserts the two binaries behave identically
(stdout + exit code). Behavioural equivalence is the sound invariant: the
two assemblers may emit different-but-valid encodings, so a byte-level
section compare would false-positive.
A true self-hosting internal-assembler fixpoint (compile the compiler with
itself via --assembler internal) is deferred: the internal assembler buffers
the whole object in memory and needs ~53 GB for the compiler's own 631k-line
.s, OOM-killing. That scalability limit is tracked in bugs.txt; until the
assembler streams its output, this differential conformance check plus
TInternalAsmE2ETests are the internal-assembler guards.
Verified: prints NATIVE_INTERNAL_OK on a fixed compiler, exits non-zero with
EXIT_MISMATCH on a compiler carrying the sret-Result bug.
0631bb0cdf