From 308bbf300fe9332130f4784c7a91fa2ad707d6e4 Mon Sep 17 00:00:00 2001
From: Abseil Team <absl-team@google.com>
Date: Tue, 6 Sep 2022 13:11:28 -0700
Subject: CMake: install artifacts reflect the compiled ABI

Change `absl/base/options.h` at install time to reflect the ABI used
to compile the libraries, i.e., if Abseil was compiled with
C++ >= 17 then the `ABSL_OPTION_USE_STD_*` macros are set to `1`,
because then the C++ 17 types are embedded in the ABI of the installed
artifacts.

Likewise, set the `target_compile_features()` of Abseil libraries
to reflect the C++ version used to compile them. If they the Abseil
libraries are compiled with C++ >= 17, then all downstream
dependencies must also be compiled with C++ >= 17.

Fixes #696

PiperOrigin-RevId: 472538165
Change-Id: Ic9e346ebe277c882a18ad96e1918c9e3511c91c3
---
 CMakeLists.txt | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

(limited to 'CMakeLists.txt')

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 706af68a..016dd917 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -46,6 +46,11 @@ if (POLICY CMP0091)
   cmake_policy(SET CMP0091 NEW)
 endif (POLICY CMP0091)
 
+# try_compile() honors the CMAKE_CXX_STANDARD value
+if (POLICY CMP0067)
+  cmake_policy(SET CMP0067 NEW)
+endif (POLICY CMP0067)
+
 project(absl LANGUAGES CXX)
 include(CTest)
 
@@ -229,4 +234,25 @@ if(ABSL_ENABLE_INSTALL)
       PATTERN "copts" EXCLUDE
       PATTERN "testdata" EXCLUDE
     )
+
+  file(READ "absl/base/options.h" ABSL_INTERNAL_OPTIONS_H_CONTENTS)
+  if (ABSL_INTERNAL_AT_LEAST_CXX17)
+    string(REGEX REPLACE
+      "#define ABSL_OPTION_USE_STD_([^ ]*) 2"
+      "#define ABSL_OPTION_USE_STD_\\1 1"
+      ABSL_INTERNAL_OPTIONS_H_PINNED
+      "${ABSL_INTERNAL_OPTIONS_H_CONTENTS}")
+  else()
+    string(REGEX REPLACE
+      "#define ABSL_OPTION_USE_STD_([^ ]*) 2"
+      "#define ABSL_OPTION_USE_STD_\\1 0"
+      ABSL_INTERNAL_OPTIONS_H_PINNED
+      "${ABSL_INTERNAL_OPTIONS_H_CONTENTS}")
+  endif()
+  file(WRITE "${CMAKE_BINARY_DIR}/options-pinned.h" "${ABSL_INTERNAL_OPTIONS_H_PINNED}")
+
+  install(FILES "${CMAKE_BINARY_DIR}/options-pinned.h"
+         DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}/absl/base
+         RENAME "options.h")
+
 endif()  # ABSL_ENABLE_INSTALL
-- 
cgit v1.2.3