Joseph Ferano
75177a5a18
The wrapper was called flan.dev.ctor, and that is a name Flan can reach: (defn dev.ctor [] i32 7) mangles onto exactly it. The program compiles and runs as a release build and fails a dev build with a redefinition clang refuses -- loud, and only under LLVM with --dev, but mangle.ml's own comment exists to make it impossible rather than loud. The name is [Mangle.dev_ctor] now and starts with the dot no reader token can produce, beside .init-globals and .init-data. The colliding program builds and prints 7. Two comments in survey.sh, both of them reasoning rather than behaviour. The counts argument against a per-name -O0 list was no argument: excluding moves the counts just as much. What actually carries it is that dies_segv builds both programs at -O0 on both backends and asserts more than this sweep would. And dev-segv's park under --dev is a forever-list reason that happens to land on a program this list already covers, not a second reason for this list. FIX.org takes the sweep, and one thing the sweep cannot say: the two heap cases of bytes-copy.flan leak 24 bytes through flan_bytes_dup, measured with --leak-check=full, and both corpora are blind to it by policy -- detect_leaks=0 on one side and --leak-check=no on the other. The row proves the copy is in bounds and written. It says nothing about who frees it, and a green sweep should not be read as though it did.
63 lines
3.3 KiB
OCaml
63 lines
3.3 KiB
OCaml
(* The symbol names a Flan build puts into an object, spelled once.
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Both backends emit the same names — that is not a nicety, it is the link:
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an [--x86] host and a redefinition module built by LLVM bind against each
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other, so [@"flan.cell.<n>"] has to be byte-for-byte the same string on
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both sides or the dlopen fails and the piece served nothing. The macro
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loader and the daemon's disassembler look up the same names from outside
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the backends entirely.
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So the prefixes live here, unquoted and without a sigil. Quoting is each
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backend's own — LLVM writes [@"..."], the assembler writes ["..."] — and a
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Flan name holds -, ?, > and /, which is why every emitted name is quoted
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at all. This module only decides *which string* is quoted.
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Not here: the ABI marker itself. [Emit.abi_marker] is ["flan.abi.llvm"] and
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[X86.abi_marker] is ["flan.abi.x86"], and the two must stay distinct —
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a crossed pair is refused at [dlopen] precisely because the marker one
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image defines is not the one the other references. Sharing that string
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would delete the mechanism. The *label* a module hangs its requirement on
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is the other half of that mechanism and is shared, so it is here: see
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[abi_require] below. *)
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(* The prefix itself. It keeps the Flan [main] from colliding with C's, and
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it is what makes every Flan symbol recognisable in a disassembly. *)
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let prefix = "flan."
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(* A function or a global. One namespace, because the language has one: a
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[defn] and a [defonce] cannot share a name, so nothing here has to keep
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them apart. The compiler's own names go through this too — [.init-globals]
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and [.init-data] start with a dot no reader token can produce. *)
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let sym n = prefix ^ n
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(* The single constructor a dev build emits, which calls the runtime's two
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enable entry points — the allocation registry and the crash handler — in
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that order. It goes through [sym] with a leading dot for exactly the reason
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that comment gives, and the reason is not decoration: the first spelling of
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this was a plain [flan.dev.ctor], which is what [(defn dev.ctor [] i32 7)]
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mangles to. That program compiles and runs as a release build and fails a
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dev build with a redefinition clang refuses. A dot is what no reader token
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can produce, so there is no Flan name that reaches this one. *)
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let dev_ctor = prefix ^ ".dev-ctor"
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(* A dev build's indirection cell: a mutable global holding the address of the
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function that is currently this name's body. *)
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let cell n = prefix ^ "cell." ^ n
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(* The two module-local caches a name the host was never built with is reached
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through — one for a function, one for a global. *)
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let cellptr n = prefix ^ "cellp." ^ n
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let globalptr n = prefix ^ "gp." ^ n
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(* A compiled macro's entry point, which the expander dlsyms by this name out
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of the module [Build.macro_module] wrote. *)
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let macro n = prefix ^ "macro." ^ n
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(* The datum a redefinition module puts its host's ABI marker into. Nothing
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outside the module names it — the relocation against the marker is the
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whole of what it does — but both backends emit it, so the string is spelled
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once here rather than twice, beside every other name that has to read the
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same on both sides. What it *holds* is each backend's own marker, and that
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pair stays distinct; see the paragraph at the top. *)
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let abi_require = prefix ^ "abi.require"
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