Re: [PATCH 3/4] unit-tests: do show relative file paths

[Phillip Wood <phillip.wood123@gmail.com>]

Hi Johannes

On 31/08/2023 07:15, Johannes Schindelin via GitGitGadget wrote:
> From: Johannes Schindelin <johannes.schindelin@gmx.de>
> 
> Visual C interpolates `__FILE__` with the absolute _Windows_ path of
> the source file. GCC interpolates it with the relative path, and the
> tests even verify that.

Oh, that's a pain

> So let's make sure that the unit tests only emit such paths.

Makes sense

> +#ifndef _MSC_VER
> +#define make_relative(location) location
> +#else
> +/*
> + * Visual C interpolates the absolute Windows path for `__FILE__`,
> + * but we want to see relative paths, as verified by t0080.
> + */
> +#include "strbuf.h"
> +#include "dir.h"
> +
> +static const char *make_relative(const char *location)
> +{
> +	static const char *prefix;
> +	static size_t prefix_len;
> +	static struct strbuf buf = STRBUF_INIT;

So far test-lib.c avoids using things like struct strbuf that it will be 
used to test. In this instance we're only using it on one particular 
compiler so it may not matter so much. We could avoid it but I'm not 
sure it is worth the extra complexity. One thing I noted in this patch 
is that prefix is leaked but I'm not sure if you run any leak checkers 
on the msvc build.

static const char *make_relative(const char *location)
{
	static char prefix[] = __FILE__
	static size_t *prefix_len = (size_t)-1;
	static char buf[PATH_MAX];

	if (prefix == (size_t)-1) {
		const char *path = "\\t\unit-tests\\test-lib.c";
		size_t path_len = strlen(path);
		
		prefix_len = strlen(prefix);
		if (prefix_len < path_len) ||
		    memcmp(prefix + prefix_len - path_len, path, path_len)
			die(...);
		prefix_len -= path_len - 1; /* keep trailing '\\' */
		prefix[prefix_len] = '\0';
	}

	/* Does it not start with the expected prefix? */
	if (fspathncmp(location, prefix, prefix_len))
		return location;

	if (strlen(location) - prefix_len > sizeof(buf) - 1)
		die(...)

	/* +1 to copy NUL terminator */
	memcpy(buf, location + prefix_len, strlen(location) - prefix_len + 1);
	convert_slashes(buf);

	return buf;
}

Best Wishes

Phillip