Merge pull request #2293 from digit-google/fix-ppoll-auto-detection
CMakeLists: Fix ppoll() feature detection.
diff --git a/CMakeLists.txt b/CMakeLists.txt
index fd32ab1..ac62a49 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -40,8 +40,16 @@
if(NOT NINJA_FORCE_PSELECT)
# Check whether ppoll() is usable on the target platform.
# Set -DUSE_PPOLL=1 if this is the case.
- include(CheckSymbolExists)
- check_symbol_exists(ppoll poll.h HAVE_PPOLL)
+ #
+ # NOTE: Use check_cxx_symbol_exists() instead of check_symbol_exists()
+ # because on Linux, <poll.h> only exposes the symbol when _GNU_SOURCE
+ # is defined.
+ #
+ # Both g++ and clang++ define the symbol by default, because the C++
+ # standard library headers require it, but *not* gcc and clang, which
+ # are used by check_symbol_exists().
+ include(CheckCXXSymbolExists)
+ check_cxx_symbol_exists(ppoll poll.h HAVE_PPOLL)
if(HAVE_PPOLL)
add_compile_definitions(USE_PPOLL=1)
endif()
