Re: git bug: Perl compatible regular expressions do not work as expected
- From
Junio C Hamano <gitster@pobox.com>
- Date
- Mar 27, 2023, 21:33 UTC
- Message-ID
- <xmqqjzz1nalp.fsf@gitster.g>
- In-Reply-To
- <03fd7ddb-8241-1a0a-3e82-d8083e4ce0f7@web.de>
René Scharfe <l.s.r@web.de> writes:
Show 6 quoted lines
> 54463d32ef only affects basic regular expressions (BRE), but -G and -S > use extended ones (ERE). macOS allows both to be "enhanced". > > I have a hard time finding a readable reference to the documentation to > brings us all onto the same page regarding what REG_ENHANCED actually > does. [1] is in raw troff format, [2] isn't very pretty and shows ads.
Wow, [2] is also misleading in that it loses the distinction between '+' and '\+'; in [1] at least you can see the differences between \&+ and \e+ ;-)
> Anyway, the rather lengthy section "ENHANCED FEATURES" explains it.
I suspect that 54463d32ef was done in a conservative way to avoid unintended side effects to make ERE "enhanced". I am not 100% certain, but after reading the documentation you pointed at, I do not see a valid expression without ENHANCED flag starting to mean totally different thing with it (well, an extra '?' turning a pattern from greedy to minimal may count as such a change in semantics, but I do not see anybody sensible adding an extra '?' in a pattern in the first place).
Perhaps it is safe to go ahead and loosen what 54463d32ef did, with something like this (this is not even compile tested, of course)?
Makefile | 9 +++++++++ compat/regcomp_enhanced.c | 2 ++ git-compat-util.h | 2 +- 3 files changed, 12 insertions(+), 1 deletion(-)
diff --git c/Makefile w/Makefile index 50ee51fde3..1fe0eb399e 100644 --- c/Makefile +++ w/Makefile @@ -293,6 +293,10 @@ include shared.mak # the flag REG_ENHANCED and you'd like to use it to enable enhanced basic # regular expressions. # +# Define USE_ENHANCED_REGULAR_EXPRESSIONS if your C library provides +# the flag REG_ENHANCED and you'd like to use it to enable enhanced +# regular expressions for both BRE and ERE. +# # Define HAVE_DEV_TTY if your system can open /dev/tty to interact with the # user. # @@ -2041,11 +2045,16 @@ ifdef NO_REGEX COMPAT_CFLAGS += -Icompat/regex COMPAT_OBJS += compat/regex/regex.o else +ifdef USE_ENHANCED_REGULAR_EXPRESSIONS + COMPAT_CFLAGS += -DUSE_ENHANCED_REGULAR_EXPRESSIONS + COMPAT_OBJS += compat/regcomp_enhanced.o +else ifdef USE_ENHANCED_BASIC_REGULAR_EXPRESSIONS COMPAT_CFLAGS += -DUSE_ENHANCED_BASIC_REGULAR_EXPRESSIONS COMPAT_OBJS += compat/regcomp_enhanced.o endif endif +endif ifdef NATIVE_CRLF BASIC_CFLAGS += -DNATIVE_CRLF endif diff --git c/compat/regcomp_enhanced.c w/compat/regcomp_enhanced.c index 84193ce53b..aadbbac6d3 100644 --- c/compat/regcomp_enhanced.c +++ w/compat/regcomp_enhanced.c @@ -3,7 +3,9 @@ int git_regcomp(regex_t *preg, const char *pattern, int cflags) { +#ifndef USE_ENHANCED_REGULAR_EXPRESSIONS if (!(cflags & REG_EXTENDED)) +#endif cflags |= REG_ENHANCED; return regcomp(preg, pattern, cflags); } diff --git c/git-compat-util.h w/git-compat-util.h index 1e6592624d..95d9b75a15 100644 --- c/git-compat-util.h +++ w/git-compat-util.h @@ -1377,7 +1377,7 @@ static inline int regexec_buf(const regex_t *preg, const char *buf, size_t size, return regexec(preg, buf, nmatch, pmatch, eflags | REG_STARTEND); } -#ifdef USE_ENHANCED_BASIC_REGULAR_EXPRESSIONS +#if defined(USE_ENHANCED_BASIC_REGULAR_EXPRESSIONS) || defined(USE_ENHANCED_REGULAR_EXPRESSIONS) int git_regcomp(regex_t *preg, const char *pattern, int cflags); #define regcomp git_regcomp #endif