PR #2104: fix: export absl::time_zone name on MinGW DLL builds Imported from GitHub PR https://github.com/abseil/abseil-cpp/pull/2104 ## Summary Building the monolithic shared library (`-DABSL_BUILD_MONOLITHIC_SHARED_LIBS=ON -DBUILD_SHARED_LIBS=ON`) with MinGW on Windows fails at link time with an undefined reference to `absl::time_internal::cctz::GetWindowsLocalTimeZone()`. That symbol lives in `time/internal/cctz/src/time_zone_name_win.cc`, which `CMake/AbseilDll.cmake` only appends to `ABSL_INTERNAL_DLL_FILES` under `if(MSVC)` - so MinGW DLL builds never compile it, even though `time_zone_lookup.cc` calls it on all Windows toolchains. This splits the single `if(MSVC) ... else() ... endif()` block into two independent conditions: the `time_zone_name_win.cc`/`.h` sources are appended under `if(WIN32)` (covering MSVC, clang-cl, and MinGW), and the `flags/*` source group stays under `if(NOT MSVC)` so MinGW keeps receiving exactly the flags sources it gets today. ## Why this matters The per-target (non-DLL) build in `absl/time/CMakeLists.txt` already gates this file on `$<$<PLATFORM_ID:Windows>:...>` - i.e. any Windows platform - so the DLL list's `MSVC`-only gate is the inconsistency. `WIN32` is the correct CMake variable here; the patch sketched in the issue comments used `if(Windows)`, which is not a variable CMake defines, so this supersedes it. A carry-along fix was merged downstream into microsoft/vcpkg (#50887), but upstream remains broken. ## Testing No C++ sources change and there is no test file for the DLL file list, so verification is a CMake configure/build matrix: the monolithic shared-library build now links under MinGW (the previously-undefined `GetWindowsLocalTimeZone()` is compiled into the DLL), and the MSVC and non-MSVC builds are unchanged (MSVC still gets the Windows time-zone source via `WIN32`; MinGW still gets the `flags/*` sources via `NOT MSVC`). Fixes #2025 Merge 2efcf3defe31ca54b74544aca4a1c2a61fa2f3d5 into 0784689a65b4ea1329fbc5174b8a57c88ec796a9 Merging this change closes #2104 COPYBARA_INTEGRATE_REVIEW=https://github.com/abseil/abseil-cpp/pull/2104 from mvanhorn:fix/2025-mingw-dll-time-zone-name-win 2efcf3defe31ca54b74544aca4a1c2a61fa2f3d5 PiperOrigin-RevId: 946043634 Change-Id: I02ca46f3d8b928ebe62d546799b0b960a1639c6c
The repository contains the Abseil C++ library code. Abseil is an open-source collection of C++ code (compliant to C++17) designed to augment the C++ standard library.
Abseil is an open-source collection of C++ library code designed to augment the C++ standard library. The Abseil library code is collected from Google's own C++ code base, has been extensively tested and used in production, and is the same code we depend on in our daily coding lives.
In some cases, Abseil provides pieces missing from the C++ standard; in others, Abseil provides alternatives to the standard for special needs we've found through usage in the Google code base. We denote those cases clearly within the library code we provide you.
Abseil is not meant to be a competitor to the standard library; we've just found that many of these utilities serve a purpose within our code base, and we now want to provide those resources to the C++ community as a whole.
If you want to just get started, make sure you at least run through the Abseil Quickstart. The Quickstart contains information about setting up your development environment, downloading the Abseil code, running tests, and getting a simple binary working.
Bazel and CMake are the official build systems for Abseil. See the quickstart for more information on building Abseil using the Bazel build system. If you require CMake support, please check the CMake build instructions and CMake Quickstart.
Abseil follows Google's Foundational C++ Support Policy. See this table for a list of currently supported versions compilers, platforms, and build tools.
Abseil contains the following C++ library components:
base base library contains initialization code and other code which all other Abseil code depends on. Code within base may not depend on any other code (other than the C++ standard library).algorithm algorithm library contains additions to the C++ <algorithm> library and container-based versions of such algorithms.cleanup cleanup library contains the control-flow-construct-like type absl::Cleanup which is used for executing a callback on scope exit.container container library contains additional STL-style containers, including Abseil's unordered “Swiss table” containers.crc The crc library contains code for computing error-detecting cyclic redundancy checks on data.debugging debugging library contains code useful for enabling leak checks, and stacktrace and symbolization utilities.flags flags library contains code for handling command line flags for libraries and binaries built with Abseil.hash hash library contains the hashing framework and default hash functor implementations for hashable types in Abseil.log log library contains LOG and CHECK macros and facilities for writing logged messages out to disk, stderr, or user-extensible destinations.memory memory library contains memory management facilities that augment C++'s <memory> library.meta meta library contains type checks similar to those available in the C++ <type_traits> library.numeric numeric library contains 128-bit integer types as well as implementations of C++20's bitwise math functions.profiling profiling library contains utility code for profiling C++ entities. It is currently a private dependency of other Abseil libraries.random random library contains functions for generating pseudorandom values.status status library contains abstractions for error handling, specifically absl::Status and absl::StatusOr<T>.strings strings library contains a variety of strings routines and utilities.synchronization synchronization library contains concurrency primitives (Abseil's absl::Mutex class, an alternative to std::mutex) and a variety of synchronization abstractions.time time library contains abstractions for computing with absolute points in time, durations of time, and formatting and parsing time within time zones.types types library contains non-container utility types.utility utility library contains utility and helper code.Abseil recommends users “live-at-head” (update to the latest commit from the master branch as often as possible). However, we realize this philosophy doesn't work for every project, so we also provide Long Term Support Releases to which we backport fixes for severe bugs. See our release management document for more details.
The Abseil C++ library is licensed under the terms of the Apache license. See LICENSE for more information.
For more information about Abseil: