h-vetinari commented on issue #48874:
URL: https://github.com/apache/arrow/issues/48874#issuecomment-3772831757
Thanks a lot! Conda-forge has the ability to backport patches where
necessary. Since `main` had barely any time to move on, and we need this change
to fix our builds, I'll definitely consider a backport. That said, looking at
the description of #48601, you're IMO going quite a bit further than would be
necessary. Not that I'm against using C++20 std facilities per se (though
they're still not completely implemented in libc++), but strictly speaking we
only need a way to use conda-forge's tzdata.
When I started down this rabbit hole, I had some first trivial changes that
looked as follows (before realizing that it's connected pretty deeply with the
vendored stuff and probably not so easy to pipe through; from that POV, I can
understand going with C++20 😅):
```diff
diff --git a/cpp/src/arrow/vendored/datetime/tz.cpp
b/cpp/src/arrow/vendored/datetime/tz.cpp
index 2cf6c62a84..27a64701a4 100644
--- a/cpp/src/arrow/vendored/datetime/tz.cpp
+++ b/cpp/src/arrow/vendored/datetime/tz.cpp
@@ -476,16 +475,19 @@ CONSTDATA auto max_day = date::December/31;
CONSTCD14 const sys_seconds min_seconds = sys_days(min_year/min_day);
-#endif // USE_OS_TZDB
-
-#ifndef _WIN32
-
static
std::string
discover_tz_dir()
{
struct stat sb;
using namespace std;
+ // this is present if we're in an activated conda environment
+ const char* condaPrefix = getenv("CONDA_PREFIX");
+ if (condaPrefix) {
+ string condaDir(condaPrefix);
+ condaDir += "/share/zoneinfo";
+ return condaDir;
+ }
# if defined(ANDROID) || defined(__ANDROID__)
CONSTDATA auto tz_dir_default = "/apex/com.android.tzdata/etc/tz";
CONSTDATA auto tz_dir_fallback = "/system/usr/share/zoneinfo";
diff --git a/cpp/src/arrow/vendored/datetime/tz.h
b/cpp/src/arrow/vendored/datetime/tz.h
index 61ab3df106..cd5fa70d29 100644
--- a/cpp/src/arrow/vendored/datetime/tz.h
+++ b/cpp/src/arrow/vendored/datetime/tz.h
@@ -82,12 +82,6 @@ static_assert(HAS_REMOTE_API == 0 ? AUTO_DOWNLOAD == 0 :
true,
# define USE_SHELL_API 1
#endif
-#if USE_OS_TZDB
-# ifdef _WIN32
-# error "USE_OS_TZDB can not be used on Windows"
-# endif
-#endif
-
#ifndef HAS_DEDUCTION_GUIDES
# if __cplusplus >= 201703
# define HAS_DEDUCTION_GUIDES 1
diff --git a/cpp/src/arrow/vendored/datetime/visibility.h
b/cpp/src/arrow/vendored/datetime/visibility.h
index 780c00d70b..cd182bdf70 100644
--- a/cpp/src/arrow/vendored/datetime/visibility.h
+++ b/cpp/src/arrow/vendored/datetime/visibility.h
@@ -17,9 +17,7 @@
#pragma once
-#ifndef _WIN32
-# define USE_OS_TZDB 1
-#endif
+#define USE_OS_TZDB 1
#if defined(ARROW_STATIC)
// intentially empty
```
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