Value of `__GLIBCXX__` for each libstdc++ release

问题

The macro __GLIBCXX__ contains the time stamp of libstdc++ releases, e.g., from gcc documentation (https://gcc.gnu.org/onlinedocs/libstdc++/manual/using_macros.html)

__GLIBCXX__ The current version of libstdc++ in compressed ISO date format, as an unsigned long. For details on the value of this particular macro for a particular release, please consult the ABI Policy and Guidelines appendix.

I am looking for the values for all releases since the release of 4.9.0 (including releases of smaller versions like 4.8.x).

The documentation of libstdc++ does not seem to provide this information (it only provides the dates up to gcc 4.7.0).

Where can I find the values of __GLIBCXX__? Does anybody have them?

The ABI Policy and Guidelines appendix (https://gcc.gnu.org/onlinedocs/libstdc++/manual/abi.html) says

Incremental bumping of a library pre-defined macro. For releases before 3.4.0, the macro is GLIBCPP. For later releases, it's GLIBCXX. (The libstdc++ project generously changed from CPP to CXX throughout its source to allow the "C" pre-processor the CPP macro namespace.) These macros are defined as the date the library was released, in compressed ISO date format, as an unsigned long.

but then only provides the values of the macro up to GCC 4.7.0. Still the day of a particular GCC releases are listed here:

https://gcc.gnu.org/releases.html

but for example for GCC 4.9.1 with release date "July 16, 2014" the ISO date format is 20140716 and the value of __GLIBCXX__ is 20140617 (notice the 7 and 6 have been switched).

回答1:

The information you want is useless anyway, so you should solve your problem a different way.

GCC 4.9.3 was released after GCC 5.3, so it has a later date in that macro, so you can't just do something like:

#if __GLIBCXX__ > 20150422 // GCC 5.1 release

because that would be true for 4.9.3, but that doesn't have all the features that 5.1 has.

Most GNU/Linux distros don't ship official FSF releases either, they build snapshots, which will have the date of the snapshot, which won't be in any list of release dates. And a snapshot from the 5.x branch on a given day will have the same date as a snapshot from the 6.x branch on a given day, so you can't tell them apart.

回答2:

In the interest of answering the original question, here's a hacky command you can execute in your shell to get the list of releases and the value of __GLIBCXX__ for each release (starting with v4.1.0):

svn list "svn://gcc.gnu.org/svn/gcc/tags" | grep -o "gcc_\([^34]_.*\|4_[^0]_.*\)_release" | xargs -n 1 -I {} sh -c "printf \"{}: \" && svn cat svn://gcc.gnu.org/svn/gcc/tags/{}/gcc/DATESTAMP"

The results are:

4.1.0: 20060228
4.1.1: 20060524
4.1.2: 20070214
4.2.0: 20070514
4.2.1: 20070719
4.2.2: 20071007
4.2.3: 20080201
4.2.4: 20080519
4.3.0: 20080305
4.3.1: 20080606
4.3.2: 20080827
4.3.3: 20090124
4.3.4: 20090804
4.3.5: 20100522
4.3.6: 20110627
4.4.0: 20090421
4.4.1: 20090722
4.4.2: 20091015
4.4.3: 20100121
4.4.4: 20100429
4.4.5: 20101001
4.4.6: 20110416
4.4.7: 20120313
4.5.0: 20100414
4.5.1: 20100731
4.5.2: 20101216
4.5.3: 20110428
4.5.4: 20120702
4.6.0: 20110325
4.6.1: 20110627
4.6.2: 20111026
4.6.3: 20120301
4.6.4: 20130412
4.7.0: 20120322
4.7.1: 20120614
4.7.2: 20120920
4.7.3: 20130411
4.7.4: 20140612
4.8.0: 20130322
4.8.1: 20130531
4.8.2: 20131016
4.8.3: 20140522
4.8.4: 20141219
4.8.5: 20150623
4.9.0: 20140422
4.9.1: 20140716
4.9.2: 20141030
4.9.3: 20150626
5.1.0: 20150422
5.2.0: 20150716
5.3.0: 20151204
6.1.0: 20160427
6.2.0: 20160822
6.3.0: 20161221
6.4.0: 20170704
7.1.0: 20170502
7.2.0: 20170814
7.3.0: 20180125

Note that these values are from the official releases from the GCC team. If you're using an unofficial release, the values might differ slightly.

回答3:

You can generate a list of possible __GLIBCXX__ values using the SVN release listing as source:

svn list --xml 'https://gcc.gnu.org/svn/gcc/tags' \
    | grep '>gcc.*release' -A4 \
    | grep 'name\|date' \
    | sed -e 's/<[^>]\+>//g' -e 's/T.*$//' -e 's/-//g' \
          -e 's/gcc_\|_release//g'  \
    | paste - -

A similar list, but more free-form and annotate with branching ascii art is maintained by the GCC team:

https://gcc.gnu.org/develop.html#timeline

Note that multiple release branches are active in parallel, cf e.g. the 4.8 and 4.9 branches:

4_8_0   20130322
4_8_1   20130531
4_8_2   20131016
4_8_3   20140522
4_8_4   20141219
4_8_5   20150623
4_9_0   20140422
4_9_1   20140716
4_9_2   20141030
4_9_3   20150626
4_9_4   20160803

Thus, unfortunately, you can't use a single date as simple cut-off value to determine a certain release.

Of course, you can auto-generate some helper macros from this list. Say - you need some workaround for the 4.8 GLIBCXX release (as used by GCC and different clang versions) then you could define a helper macro like this (after including some STL header):

#if        __GLIBCXX__ == 20130322 \
        || __GLIBCXX__ == 20130531 \
        || __GLIBCXX__ == 20131016 \
        || __GLIBCXX__ == 20140522 \
        || __GLIBCXX__ == 20141219 \
        || __GLIBCXX__ == 20150623
    #define HAVE_GLIBCXX_4_8     1
#else
    #define HAVE_GLIBCXX_4_8     0
#endif

If you are just interested in the major version and only need to support releases newer than GCC 7 than you can also use the _GLIBCXX_RELEASE macro.

来源：https://stackoverflow.com/questions/37118114/value-of-glibcxx-for-each-libstdc-release

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