Re: Bug#563882: git-core FTBFS on ia64: t1001-read-tree-m-2way.sh test fails

[Jonathan Nieder <jrnieder@gmail.com>]

Jonathan Nieder wrote:

> I have attached
> generic-is-binary.c to pin this down; could you try:
> 
> 	uname -r
> 	dpkg -l libc6
> 	gcc -Wall -W -O -o generic-is-binary generic-is-binary.c
> 	<M.out ./generic-is-binary M.out
> 
> If M.out (but not stdin) is reported to be binary, great: git is
> exonerated, and we have an independent test case.
> 
> If that doesn’t work, it would be nice to learn where the unexpected
> zero bytes are.  The attached xdiff-debug.patch asks
> "git diff --no-index M.out 4.out" which bytes it thinks are null.

Attached this time, sorry.

Jonathan

#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include <stdio.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <unistd.h>
#include <fcntl.h>

static int xprintf(const char *fmt, ...);
static int buffer_is_binary(const char *ptr, size_t size);
static int check_stdin(void);
static int check_file(const char *path);

int main(int argc, const char * const argv[])
{
	int result = 0;

	if (argc != 2) {
		fprintf(stderr, "usage: generic-is-binary <path> < <path>\n");
		exit(1);
	}

	result |= check_stdin();
	result |= check_file(argv[1]);
	return result;
}

static int buffer_is_binary(const char *ptr, size_t sz)
{
	return !!memchr(ptr, 0, sz);
}

static int check_stdin(void)
{
	static char in_buf[8000];
	char *bufp = in_buf;
	char *buf_end = in_buf + sizeof(in_buf);
	ssize_t n;

	while ((n = read(0, bufp, buf_end - bufp))) {
		if (n < 0) {
			perror("stdin: read");
			return -1;
		}
		bufp += n;
	}

	return xprintf("stdin is%s binary\n",
		buffer_is_binary(in_buf, bufp - in_buf) ?
		"" : " not");
}

static ssize_t size(const char *path)
{
	struct stat st;
	if (lstat(path, &st) < 0) {
		fprintf(stderr, "%s: lstat: %s\n",
			path, strerror(errno));
		return -1;
	}
	return st.st_size;
}

static int check_file(const char *path)
{
	ssize_t sz;
	int fd, result;
	void *data;

	if ((sz = size(path)) < 0)
		return -1;
	if ((fd = open(path, O_RDONLY)) < 0) {
		fprintf(stderr, "%s: open: %s\n",
			path, strerror(errno));
		return -1;
	}
	data = mmap(NULL, sz, PROT_READ, MAP_PRIVATE, fd, 0);
	if (data == MAP_FAILED) {
		fprintf(stderr, "%s: mmap: %s\n",
			path, strerror(errno));
		close(fd);
		return -1;
	}
	if (close(fd)) {
		fprintf(stderr, "%s: close: %s\n",
			path, strerror(errno));
		return -1;
	}

	result = xprintf("%s is%s binary\n",
		path,
		buffer_is_binary(data, sz) ?
		"" : " not");

	if (munmap(data, sz)) {
		fprintf(stderr, "%s: munmap: %s\n",
			path, strerror(errno));
		return -1;
	}
	return result;
}

static int xprintf(const char *fmt, ...)
{
	int result = 0;

	va_list ap;
	va_start(ap, fmt);
	if (vprintf(fmt, ap) < 0)
		result = -1;
	va_end(ap);
	return result;
}

diff --git a/xdiff-interface.c b/xdiff-interface.c
index 01f14fb..b5b103e 100644
--- a/xdiff-interface.c
+++ b/xdiff-interface.c
@@ -223,7 +223,15 @@ int buffer_is_binary(const char *ptr, unsigned long size)
 {
 	if (FIRST_FEW_BYTES < size)
 		size = FIRST_FEW_BYTES;
-	return !!memchr(ptr, 0, size);
+	char *null = memchr(ptr, 0, size);
+
+	fprintf(stderr, "buffer_is_binary(): ");
+	if (null)
+		fprintf(stderr, "true; first null offset: %d\n",
+			(int)(null - ptr));
+	else
+		fprintf(stderr, "false\n");
+	return !!null;
 }
 
 struct ff_regs {