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mingw: use modern strftime implementation if possible

PATCH In review Johannes Schindelin via GitGitGadget 3 participants 3 messages Apr 8, 2020 – Apr 10, 2020

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Johannes Schindelin via GitGitGadget

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PATCH 1/1 mingw: use modern strftime implementation if possible

From: =?UTF-8?q?Matthias=20A=C3=9Fhauer?= <[email protected]>

Microsoft introduced a new "Universal C Runtime Library" (UCRT) with Visual Studio 2015. The UCRT comes with a new strftime() implementation that supports more date formats. We link git against the older "Microsoft Visual C Runtime Library" (MSVCRT), so to use the UCRT strftime() we need to load it from ucrtbase.dll using DECLARE_PROC_ADDR()/INIT_PROC_ADDR().

Most supported Windows systems should have recieved the UCRT via Windows update, but in some cases only MSVCRT might be available. In that case we fall back to using that implementation.

With this change, it is possible to use e.g. the %g and %V date format specifiers, e.g.

	git show -s --format=%cd --date=format:‘%g.%V’ HEAD

Without this change, the user would see this error message on Windows:

fatal: invalid strftime format: '‘%g.%V’'

This fixes https://github.com/git-for-windows/git/issues/2495

Signed-off-by Matthias Aßhauer <[email protected]>
Signed-off-by Johannes Schindelin <[email protected]>

---
Use a modern strftime() on Windows when available

This is another contribution that came in via Git for Windows.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-753%2Fdscho%2Fmingw-modern-strftime-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-753/dscho/mingw-modern-strftime-v1
Pull-Request: https://github.com/git/git/pull/753

 compat/mingw.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)
compat/mingw.c +10 -1
index d14065d60ec..2136744af35 100644
@@ -964,7 +964,16 @@ int mingw_utime (const char *file_name, const struct utimbuf *times)
 size_t mingw_strftime(char *s, size_t max,
 		      const char *format, const struct tm *tm)
 {
-	size_t ret = strftime(s, max, format, tm);
+	/* a pointer to the original strftime in case we can't find the UCRT version */
+	static size_t (*fallback)(char *, size_t, const char *, const struct tm *) = strftime;
+	size_t ret;
+	DECLARE_PROC_ADDR(ucrtbase.dll, size_t, strftime, char *, size_t,
+		const char *, const struct tm *);
+
+	if (INIT_PROC_ADDR(strftime))
+		ret = strftime(s, max, format, tm);
+	else
+		ret = fallback(s, max, format, tm);
 
 	if (!ret && errno == EINVAL)
 		die("invalid strftime format: '%s'", format);

base-commit: 9fadedd637b312089337d73c3ed8447e9f0aa775

Signature · 1 line
gitgitgadget
#1 lore raw

"Johannes Schindelin via GitGitGadget" <[email protected]>

Quoted 22 lines · writes:

From: =?UTF-8?q?Matthias=20A=C3=9Fhauer?= <[email protected]>

Microsoft introduced a new "Universal C Runtime Library" (UCRT) with Visual Studio 2015. The UCRT comes with a new strftime() implementation that supports more date formats. We link git against the older "Microsoft Visual C Runtime Library" (MSVCRT), so to use the UCRT strftime() we need to load it from ucrtbase.dll using DECLARE_PROC_ADDR()/INIT_PROC_ADDR().

Most supported Windows systems should have recieved the UCRT via Windows update, but in some cases only MSVCRT might be available. In that case we fall back to using that implementation.

With this change, it is possible to use e.g. the %g and %V date format specifiers, e.g.

	git show -s --format=%cd --date=format:‘%g.%V’ HEAD

Without this change, the user would see this error message on Windows:

fatal: invalid strftime format: '‘%g.%V’'

Quoted 8 lines

This fixes https://github.com/git-for-windows/git/issues/2495

Signed-off-by Matthias Aßhauer <[email protected]>
Signed-off-by Johannes Schindelin <[email protected]>

---
Use a modern strftime() on Windows when available

This is another contribution that came in via Git for Windows.

Sure. It would be very surprising if contribution to compat/mingw.c came in via Git on Macintosh ;-)

Will apply, together with the other one. Thanks.

#2 lore raw

Hi Junio,

Quoted 32 lines · Junio C Hamano

"Johannes Schindelin via GitGitGadget" <[email protected]>

Quoted 29 lines · writes:

From: =?UTF-8?q?Matthias=20A=C3=9Fhauer?= <[email protected]>

Microsoft introduced a new "Universal C Runtime Library" (UCRT) with Visual Studio 2015. The UCRT comes with a new strftime() implementation that supports more date formats. We link git against the older "Microsoft Visual C Runtime Library" (MSVCRT), so to use the UCRT strftime() we need to load it from ucrtbase.dll using DECLARE_PROC_ADDR()/INIT_PROC_ADDR().

Most supported Windows systems should have recieved the UCRT via Windows update, but in some cases only MSVCRT might be available. In that case we fall back to using that implementation.

With this change, it is possible to use e.g. the %g and %V date format specifiers, e.g.

	git show -s --format=%cd --date=format:‘%g.%V’ HEAD

Without this change, the user would see this error message on Windows:

fatal: invalid strftime format: '‘%g.%V’'

This fixes https://github.com/git-for-windows/git/issues/2495

Signed-off-by Matthias Aßhauer <[email protected]>
Signed-off-by Johannes Schindelin <[email protected]>

---
Use a modern strftime() on Windows when available

Quoted 4 lines
Quoted 1 line

This is another contribution that came in via Git for Windows.

Sure. It would be very surprising if contribution to compat/mingw.c came in via Git on Macintosh ;-)

What I mean to say with this is that the patches have seen some real-life testing.

Quoted 1 line

Will apply, together with the other one. Thanks.

Thanks,
Dscho