test: add tmpfile.c

Though `wasi-libc` may not want to expose `tmpfile` and other related,
Unix-specific, "create a /tmp thing" functions, these functions are
quite useful during testing. By pulling in slightly-altered versions of
these functions, this change also enables two new tests, `fdopen.c` and
`ungetc.c`.

test/Makefile

@@ -98,6 +98,12 @@ INFRA_WASM_OBJS := $(patsubst $(LIBC_TEST)/src/common/%.c,$(OBJDIR)/common/%.was
 $(OBJDIR)/common/%.wasm.o: $(LIBC_TEST)/src/common/%.c | $(INFRA_OBJDIR)
 	$(CC) $(CFLAGS) -c $< -o $@
 
+# In some cases, we need extra test infrastructure to provide some unimplemented
+# functions (see the `common` directory).
+INFRA_WASM_OBJS += $(OBJDIR)/common/tmpfile.wasm.o
+$(OBJDIR)/common/tmpfile.wasm.o: common/tmpfile.c | $(INFRA_OBJDIR)
+	$(CC) $(CFLAGS) -c $< -o $@
+
 # Also, include the `libc-test` infrastructure headers.
 INFRA_HEADERS_DIR := $(LIBC_TEST)/src/common
 INFRA_HEADERS := $(shell find $(INFRA_HEADERS_DIR) -name '*.h')

test/common/tmpfile.c

@@ -0,0 +1,86 @@
+/*
+ * For tests that need to create temporary files, it is quite convenient to
+ * implement the following functions. Note that these are to be used as testing
+ * infrastructure (i.e., creating files to test against), not for testing the
+ * implementation of these functions themselves which may be altered slightly.
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <string.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <unistd.h>
+
+/*
+ * Copied from `libc-top-half/musl/src/temp/__randname.c`. This assumes that a
+   check for the template size has already been made
+ */
+char *__randname(char *template)
+{
+	int i;
+	struct timespec ts;
+	unsigned long r;
+
+	clock_gettime(CLOCK_REALTIME, &ts);
+	r = ts.tv_nsec*65537 ^ (uintptr_t)&ts / 16 + (uintptr_t)template;
+	for (i=0; i<6; i++, r>>=5)
+		template[i] = 'A'+(r&15)+(r&16)*2;
+
+	return template;
+}
+
+/*
+ * Adapted from `libc-top-half/musl/src/stdio/tmpfile.c`; this implementation
+ * does not retry opening the file.
+ */
+#define MAXTRIES 1
+FILE *tmpfile(void)
+{
+	char s[] = "/tmp/tmpfile_XXXXXX";
+	int fd;
+	FILE *f;
+	int try;
+	for (try=0; try<MAXTRIES; try++) {
+		__randname(s+5);
+		fd = open(s, O_RDWR|O_CREAT|O_EXCL, 0600);
+		if (fd >= 0) {
+            unlink(s);
+			f = fdopen(fd, "w+");
+			if (!f) close(fd);
+			return f;
+		}
+	}
+	return 0;
+}
+
+/*
+ * Adapted from `libc-top-half/musl/src/stdio/mkostemps.c` and
+ * `libc-top-half/musl/src/temp/mkstemp.c`; this implementation does not
+ * actually retry creating the file.
+ */
+int __mkostemps(char *template, int len, int flags)
+{
+	size_t l = strlen(template);
+	if (l<6 || len>l-6 || memcmp(template+l-len-6, "XXXXXX", 6)) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	flags -= flags & O_ACCMODE;
+	int fd, retries = 1;
+	do {
+		__randname(template+l-len-6);
+		if ((fd = open(template, flags | O_RDWR | O_CREAT | O_EXCL, 0600))>=0)
+			return fd;
+	} while (--retries && errno == EEXIST);
+
+	memcpy(template+l-len-6, "XXXXXX", 6);
+	return -1;
+}
+int mkstemp(char *template)
+{
+	return __mkostemps(template, 0, 0);
+}

test/common/tmpfile.h

@@ -0,0 +1,7 @@
+/*
+ * For tests that need to create temporary files, it is quite convenient to
+ * implement the following functions; see `tmpfile.c` for details.
+ */
+#include <stdio.h>
+FILE *tmpfile(void);
+int mkstemp(char *);

test/src/libc-test/functional/fdopen.c

@@ -0,0 +1,3 @@
+// add-flags.py(CFLAGS): -I. -include common/tmpfile.h
+// add-flags.py(RUN): --dir fs::/tmp
+#include "build/download/libc-test/src/functional/fdopen.c"

test/src/libc-test/functional/ungetc.c

@@ -0,0 +1,3 @@
+// add-flags.py(CFLAGS): -I. -include common/tmpfile.h
+// add-flags.py(RUN): --dir fs::/tmp
+#include "build/download/libc-test/src/functional/ungetc.c"