ww: preserve compiler sink outputs

cmd/w6c/main.c

@@ -13,6 +13,7 @@ struct publication {
 	char *backup;
 	int had_old;
 	int installed;
+	int passthrough;
 };
 
 static char *
@@ -30,9 +31,37 @@ publish_path(const char *dst, const char *kind)
 	return p;
 }
 
+static int
+copy_stream(FILE *src, FILE *out)
+{
+	int bad = fflush(src) != 0 || fseek(src, 0, SEEK_SET) != 0;
+	unsigned char buf[65536];
+	while (!bad) {
+		size_t n = fread(buf, 1, sizeof buf, src);
+		if (n != 0 && fwrite(buf, 1, n, out) != n) bad = 1;
+		if (n < sizeof buf) {
+			if (ferror(src)) bad = 1;
+			break;
+		}
+	}
+	return bad ? -1 : 0;
+}
+
 static int
 materialize_stream(FILE *src, struct publication *p)
 {
+	struct stat st;
+	if (lstat(p->dst, &st) == 0 && S_ISCHR(st.st_mode)) {
+		FILE *out = fopen(p->dst, "wb");
+		int bad = out == NULL || copy_stream(src, out) < 0;
+		if (out != NULL && fclose(out) != 0) bad = 1;
+		if (bad) {
+			fprintf(stderr, "w6c: cannot write %s\n", p->dst);
+			return -1;
+		}
+		p->passthrough = 1;
+		return 0;
+	}
 	p->stage = publish_path(p->dst, "new");
 	p->backup = publish_path(p->dst, "old");
 	if (p->stage == NULL || p->backup == NULL) {
@@ -50,16 +79,7 @@ materialize_stream(FILE *src, struct publication *p)
 		unlink(p->stage);
 		return -1;
 	}
-	int bad = fflush(src) != 0 || fseek(src, 0, SEEK_SET) != 0;
+	int bad = copy_stream(src, out) < 0;
-	unsigned char buf[65536];
-	while (!bad) {
-		size_t n = fread(buf, 1, sizeof buf, src);
-		if (n != 0 && fwrite(buf, 1, n, out) != n) bad = 1;
-		if (n < sizeof buf) {
-			if (ferror(src)) bad = 1;
-			break;
-		}
-	}
 	if (fclose(out) != 0) bad = 1;
 	if (bad) {
 		unlink(p->stage);
@@ -100,6 +120,7 @@ static int
 publish_all(struct publication *p, int n)
 {
 	for (int i = 0; i < n; i++) {
+		if (p[i].passthrough) continue;
 		if (!path_is_regular_nofollow(p[i].stage)) {
 			fprintf(stderr, "w6c: publication stage is not a regular file for %s\n",
 			    p[i].dst);
@@ -120,6 +141,7 @@ publish_all(struct publication *p, int n)
 		}
 	}
 	for (int i = 0; i < n; i++) {
+		if (p[i].passthrough) continue;
 		int exists = path_exists_nofollow(p[i].backup);
 		if (exists != 0) {
 			if (exists < 0)
@@ -132,6 +154,7 @@ publish_all(struct publication *p, int n)
 		}
 	}
 	for (int i = 0; i < n; i++) {
+		if (p[i].passthrough) continue;
 		if (rename(p[i].dst, p[i].backup) == 0)
 			p[i].had_old = 1;
 		else if (errno != ENOENT) {
@@ -140,6 +163,7 @@ publish_all(struct publication *p, int n)
 		}
 	}
 	for (int i = 0; i < n; i++) {
+		if (p[i].passthrough) continue;
 		if (rename(p[i].stage, p[i].dst) != 0) {
 			fprintf(stderr, "w6c: cannot publish %s\n", p[i].dst);
 			goto rollback;
@@ -149,13 +173,15 @@ publish_all(struct publication *p, int n)
 	/* Installation is the commit point.  Backup cleanup cannot truthfully
 	 * turn a completely installed pair into a rejected compilation. */
 	for (int i = 0; i < n; i++)
-		if (p[i].had_old && unlink(p[i].backup) != 0) {
+		if (!p[i].passthrough && p[i].had_old
+		    && unlink(p[i].backup) != 0) {
 			fprintf(stderr, "w6c: cannot remove backup for %s\n", p[i].dst);
 		}
 	return 0;
 
 rollback:
 	for (int i = n - 1; i >= 0; i--) {
+		if (p[i].passthrough) continue;
 		if (p[i].installed) (void)unlink(p[i].dst);
 		if (p[i].had_old) (void)rename(p[i].backup, p[i].dst);
 		if (p[i].stage != NULL) (void)unlink(p[i].stage);

docs/build-system.md

@@ -5147,10 +5147,12 @@ and is never followed or removed. A committed dispatcher voucher must itself
 be a regular file before it can authorize reuse. Compiler assembly and
 interface bytes are first generated through anonymous files with checked full
 writes and then published as their own rollback group. A non-regular compiler
-destination is rejected before preservation, and installation—not cleanup of
+destination is rejected before preservation, except that an already existing
-a recoverable old backup—is the commit point. Cold rejection removes the exact
+character-device sink such as `/dev/null` receives a checked passthrough and is
-request-owned scratch tree. Stale init code, stale closure metadata, and mixed
+never renamed or treated as a persistent artifact. Installation—not cleanup
-committed generations therefore cannot be reused.
+of a recoverable old backup—is the commit point. Cold rejection removes the
+exact request-owned scratch tree. Stale init code, stale closure metadata, and
+mixed committed generations therefore cannot be reused.
 
 #### Stage and observer ownership
 

selfhost/cmd/w6c/main.ww

@@ -14,6 +14,7 @@ type publication = struct {
 	backup: str,
 	hadold: bool,
 	installed: bool,
+	passthrough: bool,
 };
 
 fn publicationpath(dst: *u8, kind: str) str = {
@@ -21,6 +22,17 @@ fn publicationpath(dst: *u8, kind: str) str = {
 		strconv.i32tos(os.getpid(), strconv.base.DEC), ".", kind);
 };
 
+fn pathischardevice(path: *u8) bool = {
+	let fi: os.filestat;
+	match (os.lstat(&fi, pathstr(path))) {
+	case void => {
+		return (((fi.mode: u32) & 61440u32) == (os.mode.CHR: u32));
+	};
+	case let e: os.oserror => return false;
+	};
+	return false;
+};
+
 // Open a destination-adjacent file and immediately unlink its name. Cgen's
 // fatal exit then leaves only a kernel-owned fd, never a partial destination
 // or named staging artifact.
@@ -28,6 +40,12 @@ fn anonymousfd(dst: *u8, kind: str) i32 = {
 	let path: str = publicationpath(dst, kind);
 	let fd: i32 = os.open(path,
 		os.flag.RDWR | os.flag.CREATE | os.flag.EXCL, 384i32);
+	if (fd < 0 && pathischardevice(dst)) {
+		path = strings.concat("/tmp/ww-w6c.",
+			strconv.i32tos(os.getpid(), strconv.base.DEC), ".", kind);
+		fd = os.open(path,
+			os.flag.RDWR | os.flag.CREATE | os.flag.EXCL, 384i32);
+	};
 	if (fd < 0) {
 		os.write(2, "w6c: cannot create anonymous output\n".ptr,
 			"w6c: cannot create anonymous output\n".len: u64);
@@ -60,6 +78,21 @@ fn copystream(src: i32, dst: i32) bool = {
 
 fn materializestream(src: i32, dst: *u8, p: *publication) bool = {
 	p.dst = dst;
+	p.passthrough = false;
+	let fi: os.filestat;
+	match (os.lstat(&fi, pathstr(dst))) {
+	case void => {
+		if (((fi.mode: u32) & 61440u32) == (os.mode.CHR: u32)) {
+			let sink: i32 = os.open(pathstr(dst), os.flag.WRONLY, 0i32);
+			if (sink < 0) { return false; };
+			let sinkok: bool = copystream(src, sink);
+			if (os.close(sink) != 0) { sinkok = false; };
+			if (sinkok) { p.passthrough = true; };
+			return sinkok;
+		};
+	};
+	case let e: os.oserror => void;
+	};
 	p.stage = publicationpath(dst, "new");
 	p.backup = publicationpath(dst, "old");
 	p.hadold = false;
@@ -110,6 +143,7 @@ fn publishall(p: *publication, n: i32) bool = {
 	let i: i32 = 0;
 	let ok: bool = true;
 	for (i < n) {
+		if (p[i].passthrough) { i += 1; continue; };
 		if (!pathisregularnofollow(p[i].stage)) {
 			publishdiag("w6c: publication stage is not a regular file for ",
 				p[i].dst);
@@ -140,6 +174,7 @@ fn publishall(p: *publication, n: i32) bool = {
 	if (ok) {
 		i = 0;
 		for (i < n) {
+			if (p[i].passthrough) { i += 1; continue; };
 			let exists: i32 = pathexistsnofollow(p[i].backup);
 			if (exists != 0) {
 				if (exists < 0) {
@@ -157,6 +192,7 @@ fn publishall(p: *publication, n: i32) bool = {
 	if (ok) {
 		i = 0;
 		for (i < n) {
+			if (p[i].passthrough) { i += 1; continue; };
 			let rc: i32 = os.rename(pathstr(p[i].dst), p[i].backup);
 			if (rc == 0) { p[i].hadold = true; }
 			else { if (rc != -2) {
@@ -170,6 +206,7 @@ fn publishall(p: *publication, n: i32) bool = {
 	if (ok) {
 		i = 0;
 		for (i < n) {
+			if (p[i].passthrough) { i += 1; continue; };
 			if (os.rename(p[i].stage, pathstr(p[i].dst)) != 0) {
 				publishdiag("w6c: cannot publish ", p[i].dst);
 				ok = false;
@@ -183,7 +220,8 @@ fn publishall(p: *publication, n: i32) bool = {
 			// truthfully turn a completely installed pair into rejection.
 			i = 0;
 			for (i < n) {
-				if (p[i].hadold && os.remove(p[i].backup) != 0) {
+				if (!p[i].passthrough && p[i].hadold
+				    && os.remove(p[i].backup) != 0) {
 					publishdiag("w6c: cannot remove backup for ", p[i].dst);
 				};
 				i += 1;
@@ -193,6 +231,7 @@ fn publishall(p: *publication, n: i32) bool = {
 	};
 	i = n - 1;
 	for (i >= 0) {
+		if (p[i].passthrough) { i -= 1; continue; };
 		if (p[i].installed) { os.remove(pathstr(p[i].dst)); };
 		if (p[i].hadold) { os.rename(p[i].backup, pathstr(p[i].dst)); };
 		if (p[i].stage.len != 0) { os.remove(p[i].stage); };
@@ -882,6 +921,7 @@ export fn main(argc: i32, argv: **u8) i32 = {
 		pubs[pi].backup = "";
 		pubs[pi].hadold = false;
 		pubs[pi].installed = false;
+		pubs[pi].passthrough = false;
 		pi += 1;
 	};
 	let npub: i32 = 0;