[musl] [PATCH] fix glibc ABI compat

[Szabolcs Nagy <nsz@port70.net>]

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i recently run into a missing glibc abi compat symbol
when trying to run a glibc linked executable with musl.

__strftime_l is at least used by glibc linked libstdc++
but glibc linked libstdc++ can have compatibility issues
with musl so it's not clear how commonly it is useful.

likewise i don't know how likely the glibc libresolv
symbols may be useful to have in musl.

but it does not seem to hurt to have these exported.

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From 6e8e7105d210f195caf93422f6b9d880e7cc0cc0 Mon Sep 17 00:00:00 2001
From: Szabolcs Nagy <nsz@port70.net>
Date: Sat, 28 Mar 2020 11:11:32 +0000
Subject: [PATCH] fix glibc ABI compat

commit 0676c3a34c7bf12b33f8f5efb92476f4ffc7f20e made various
internal symbols hidden, but some of those symbols are useful
for glibc ABI compatibility (e.g. __nl_langinfo_l is internal
but was not made hidden).

following symbols are hidden in musl, but exported in glibc:

__clock_gettime
__clone
__dn_expand
__getauxval
__gmtime_r
__lseek
__madvise
__mmap
__mprotect
__munmap
__pthread_key_create
__pthread_mutex_lock
__pthread_mutex_trylock
__pthread_mutex_unlock
__pthread_once
__pthread_rwlock_rdlock
__pthread_rwlock_tryrdlock
__pthread_rwlock_trywrlock
__pthread_rwlock_unlock
__pthread_rwlock_wrlock
__res_mkquery
__res_send
__sigaction
__stpcpy
__stpncpy
__strftime_l
__wait

at least the following symbols appear in glibc installed headers
currently so binaries can plausably end up using them:

__dn_expand
__res_mkquery
__res_send
__stpcpy
__stpncpy

and it is known that glibc linked libstdc++ uses

__strftime_l

it seems there never was a redirection to __stpcpy or __stpncpy
in glibc headers and there is no known direct usage of them so
they are kept hidden in musl.
---
 src/include/resolv.h | 6 +++---
 src/include/time.h   | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/include/resolv.h b/src/include/resolv.h
index 945e89e6..6387adca 100644
--- a/src/include/resolv.h
+++ b/src/include/resolv.h
@@ -3,10 +3,10 @@
 
 #include "../../include/resolv.h"
 
-hidden int __dn_expand(const unsigned char *, const unsigned char *, const unsigned char *, char *, int);
+int __dn_expand(const unsigned char *, const unsigned char *, const unsigned char *, char *, int);
 
-hidden int __res_mkquery(int, const char *, int, int, const unsigned char *, int, const unsigned char*, unsigned char *, int);
-hidden int __res_send(const unsigned char *, int, unsigned char *, int);
+int __res_mkquery(int, const char *, int, int, const unsigned char *, int, const unsigned char*, unsigned char *, int);
+int __res_send(const unsigned char *, int, unsigned char *, int);
 hidden int __res_msend(int, const unsigned char *const *, const int *, unsigned char *const *, int *, int);
 
 #endif
diff --git a/src/include/time.h b/src/include/time.h
index cbabde47..4f94bc39 100644
--- a/src/include/time.h
+++ b/src/include/time.h
@@ -10,6 +10,6 @@ hidden char *__asctime_r(const struct tm *, char *);
 hidden struct tm *__gmtime_r(const time_t *restrict, struct tm *restrict);
 hidden struct tm *__localtime_r(const time_t *restrict, struct tm *restrict);
 
-hidden size_t __strftime_l(char *restrict, size_t, const char *restrict, const struct tm *restrict, locale_t);
+size_t __strftime_l(char *restrict, size_t, const char *restrict, const struct tm *restrict, locale_t);
 
 #endif
-- 
2.24.1