CheckSymbolExists: Work around GCC failure with -pedantic-errors option

GCC mistakenly issues the pedantic warning "ISO C forbids conversion of
function pointer to object pointer type". With -pedantic-errors in the
compile flags, that diagnostic prevents check_symbol_exists() from
detecting function symbols.

The solution is to filter out -pedantic-errors (and -Werror, just to be
future proof) before invoking try_compile().

Fixes: #13208

1 files changed, 11 insertions, 0 deletions

diff --git a/Tests/CMakeOnly/CheckSymbolExists/CMakeLists.txt b/Tests/CMakeOnly/CheckSymbolExists/CMakeLists.txt
index 9a9bb2a395..3d65b7ab18 100644
--- a/Tests/CMakeOnly/CheckSymbolExists/CMakeLists.txt
+++ b/Tests/CMakeOnly/CheckSymbolExists/CMakeLists.txt
@@ -48,4 +48,15 @@ if (CMAKE_COMPILER_IS_GNUCC)
   if (CSE_RESULT_O3)
     message(SEND_ERROR "CheckSymbolExists reported a nonexistent symbol as existing with optimization -O3")
   endif ()
+
+  string(APPEND CMAKE_C_FLAGS " -pedantic-errors")
+  unset(CS_RESULT_PEDANTIC_ERRORS CACHE)
+  message(STATUS "Testing with -pedantic-errors")
+
+  check_symbol_exists(fopen "stdio.h" CSE_RESULT_PEDANTIC_ERRORS)
+
+  if(NOT CSE_RESULT_PEDANTIC_ERRORS)
+    message(SEND_ERROR "CheckSymbolExists reported an existing symbol as nonexisting with -pedantic-errors")
+  endif()
+
 endif ()