Re: [PATCH v2] unit-tests: do show relative file paths on non-Windows, too

>> There is a larger clean-up opportunity to drop the need for making a
>> copy, which probably is worth doing, so I folded the above into this
>> version.
>
> Ooh, that's nice. This version looks good, I found the code comments
> very helpful

> Best Wishes
>
> Phillip
>
>> ------- >8 ------------- >8 ------------- >8 ------------- >8 -------
>> There are compilers other than Visual C that want to show absolute
>> paths.  Generalize the helper introduced by a2c5e294 (unit-tests: do
>> show relative file paths, 2023-09-25) so that it can also work with
>> a path that uses slash as the directory separator, and becomes
>> almost no-op once one-time preparation finds out that we are using a
>> compiler that already gives relative paths.  Incidentally, this also
>> should do the right thing on Windows with a compiler that shows
>> relative paths but with backslash as the directory separator (if
>> such a thing exists and is used to build git).
>> Reported-by: Randall S. Becker <rsbecker@nexbridge.com>
>> Helped-by: Phillip Wood <phillip.wood@dunelm.org.uk>
>> Signed-off-by: Junio C Hamano <gitster@pobox.com>
>> ---
>>    * I found that the diff relative to the result of applying v1 was
>>      easier to follow than the range-diff, so here it is.
>>    diff --git c/t/unit-tests/test-lib.c w/t/unit-tests/test-lib.c
>>    index 83c9eb8c59..66d6980ffb 100644
>>    --- c/t/unit-tests/test-lib.c
>>    +++ w/t/unit-tests/test-lib.c
>>    @@ -64,34 +64,33 @@ static const char *make_relative(const char *location)
>>     		 * prefix_len == 0 if the compiler gives paths relative
>>     		 * to the root of the working tree.  Otherwise, we want
>>     		 * to see that we did find the needle[] at a directory
>>    -		 * boundary.
>>    +		 * boundary.  Again we rely on that needle[] begins with
>>    +		 * "t" followed by the directory separator.
>>     		 */
>>     		if (fspathcmp(needle, prefix + prefix_len) ||
>>    -		    (prefix_len &&
>>    -		     prefix[prefix_len - 1] != '/' &&
>>    -		     prefix[prefix_len - 1] != '\\'))
>>    +		    (prefix_len && prefix[prefix_len - 1] != needle[1]))
>>     			die("unexpected suffix of '%s'", prefix);
>>    -
>>     	}
>>         	/*
>>    -	 * If our compiler gives relative paths and we do not need
>>    -	 * to munge directory separator, we can return location as-is.
>>    +	 * Does it not start with the expected prefix?
>>    +	 * Return it as-is without making it worse.
>>     	 */
>>    -	if (!prefix_len && !need_bs_to_fs)
>>    +	if (prefix_len && fspathncmp(location, prefix, prefix_len))
>>     		return location;
>>        -	/* Does it not start with the expected prefix? */
>>    -	if (fspathncmp(location, prefix, prefix_len))
>>    -		return location;
>>    +	/*
>>    +	 * If we do not need to munge directory separator, we can return
>>    +	 * the substring at the tail of the location.
>>    +	 */
>>    +	if (!need_bs_to_fs)
>>    +		return location + prefix_len;
>>        -	strlcpy(buf, location + prefix_len, sizeof(buf));
>>     	/* convert backslashes to forward slashes */
>>    -	if (need_bs_to_fs) {
>>    -		for (p = buf; *p; p++)
>>    -			if (*p == '\\')
>>    -				*p = '/';
>>    -	}
>>    +	strlcpy(buf, location + prefix_len, sizeof(buf));
>>    +	for (p = buf; *p; p++)
>>    +		if (*p == '\\')
>>    +			*p = '/';
>>     	return buf;
>>     }
>>       t/unit-tests/test-lib.c | 61
>> +++++++++++++++++++++++++++++++----------
>>   1 file changed, 47 insertions(+), 14 deletions(-)
>> diff --git a/t/unit-tests/test-lib.c b/t/unit-tests/test-lib.c
>> index 7bf9dfdb95..66d6980ffb 100644
>> --- a/t/unit-tests/test-lib.c
>> +++ b/t/unit-tests/test-lib.c
>> @@ -21,12 +21,11 @@ static struct {
>>   	.result = RESULT_NONE,
>>   };
>>   -#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.
>> + * There are other compilers that do the same, and are not for
>> + * Windows.
>>    */
>>   #include "dir.h"
>>   @@ -34,32 +33,66 @@ static const char *make_relative(const char
>> *location)
>>   {
>>   	static char prefix[] = __FILE__, buf[PATH_MAX], *p;
>>   	static size_t prefix_len;
>> +	static int need_bs_to_fs = -1;
>>   -	if (!prefix_len) {
>> +	/* one-time preparation */
>> +	if (need_bs_to_fs < 0) {
>>   		size_t len = strlen(prefix);
>> -		const char *needle = "\\t\\unit-tests\\test-lib.c";
>> +		char needle[] = "t\\unit-tests\\test-lib.c";
>>   		size_t needle_len = strlen(needle);
>>   -		if (len < needle_len || strcmp(needle, prefix + len -
>> needle_len))
>> -			die("unexpected suffix of '%s'", prefix);
>> +		if (len < needle_len)
>> +			die("unexpected prefix '%s'", prefix);
>> +
>> +		/*
>> +		 * The path could be relative (t/unit-tests/test-lib.c)
>> +		 * or full (/home/user/git/t/unit-tests/test-lib.c).
>> +		 * Check the slash between "t" and "unit-tests".
>> +		 */
>> +		prefix_len = len - needle_len;
>> +		if (prefix[prefix_len + 1] == '/') {
>> +			/* Oh, we're not Windows */
>> +			for (size_t i = 0; i < needle_len; i++)
>> +				if (needle[i] == '\\')
>> +					needle[i] = '/';
>> +			need_bs_to_fs = 0;
>> +		} else {
>> +			need_bs_to_fs = 1;
>> +		}
>>   -		/* let it end in a directory separator */
>> -		prefix_len = len - needle_len + 1;
>> +		/*
>> +		 * prefix_len == 0 if the compiler gives paths relative
>> +		 * to the root of the working tree.  Otherwise, we want
>> +		 * to see that we did find the needle[] at a directory
>> +		 * boundary.  Again we rely on that needle[] begins with
>> +		 * "t" followed by the directory separator.
>> +		 */
>> +		if (fspathcmp(needle, prefix + prefix_len) ||
>> +		    (prefix_len && prefix[prefix_len - 1] != needle[1]))
>> +			die("unexpected suffix of '%s'", prefix);
>>   	}
>>   -	/* Does it not start with the expected prefix? */
>> -	if (fspathncmp(location, prefix, prefix_len))
>> +	/*
>> +	 * Does it not start with the expected prefix?
>> +	 * Return it as-is without making it worse.
>> +	 */
>> +	if (prefix_len && fspathncmp(location, prefix, prefix_len))
>>   		return location;
>>   -	strlcpy(buf, location + prefix_len, sizeof(buf));
>> +	/*
>> +	 * If we do not need to munge directory separator, we can return
>> +	 * the substring at the tail of the location.
>> +	 */
>> +	if (!need_bs_to_fs)
>> +		return location + prefix_len;
>> +
>>   	/* convert backslashes to forward slashes */
>> +	strlcpy(buf, location + prefix_len, sizeof(buf));
>>   	for (p = buf; *p; p++)
>>   		if (*p == '\\')
>>   			*p = '/';
>> -
>>   	return buf;
>>   }
>> -#endif
>>     static void msg_with_prefix(const char *prefix, const char
>> *format, va_list ap)
>>   {