try_compile: Escape CMAKE_<lang>_FLAGS in test projects (#14268)

If CMAKE_<lang>_FLAGS contains quotes or other CMake language characters
they must be escaped when written into the generated CMakeLists.txt file
so that the test project parses them properly.

Teach the TryCompile test to cover this case by adding a flag with
quotes into CMAKE_C_FLAGS during a C language try_compile.

Source/cmCoreTryCompile.cxx

@@ -12,6 +12,7 @@
 #include "cmCoreTryCompile.h"
 #include "cmake.h"
 #include "cmCacheManager.h"
+#include "cmLocalGenerator.h"
 #include "cmGlobalGenerator.h"
 #include "cmExportTryCompileFileGenerator.h"
 #include <cmsys/Directory.hxx>
@@ -214,8 +215,8 @@ int cmCoreTryCompile::TryCompileCode(std::vector<std::string> const& argv)
       }
 
     // Detect languages to enable.
-    cmGlobalGenerator* gg =
-      this->Makefile->GetCMakeInstance()->GetGlobalGenerator();
+    cmLocalGenerator* lg = this->Makefile->GetLocalGenerator();
+    cmGlobalGenerator* gg = lg->GetGlobalGenerator();
     std::set<std::string> testLangs;
     for(std::vector<std::string>::iterator si = sources.begin();
         si != sources.end(); ++si)
@@ -295,13 +296,12 @@ int cmCoreTryCompile::TryCompileCode(std::vector<std::string> const& argv)
     for(std::set<std::string>::iterator li = testLangs.begin();
         li != testLangs.end(); ++li)
       {
-      fprintf(fout, "SET(CMAKE_%s_FLAGS \"", li->c_str());
       std::string langFlags = "CMAKE_" + *li + "_FLAGS";
-      if(const char* flags = this->Makefile->GetDefinition(langFlags.c_str()))
-        {
-        fprintf(fout, " %s ", flags);
-        }
-      fprintf(fout, " ${COMPILE_DEFINITIONS}\")\n");
+      const char* flags = this->Makefile->GetDefinition(langFlags.c_str());
+      fprintf(fout, "SET(CMAKE_%s_FLAGS %s)\n", li->c_str(),
+              lg->EscapeForCMake(flags?flags:"").c_str());
+      fprintf(fout, "SET(CMAKE_%s_FLAGS \"${CMAKE_%s_FLAGS}"
+              " ${COMPILE_DEFINITIONS}\")\n", li->c_str(), li->c_str());
       }
     fprintf(fout, "INCLUDE_DIRECTORIES(${INCLUDE_DIRECTORIES})\n");
     fprintf(fout, "SET(CMAKE_SUPPRESS_REGENERATION 1)\n");

Tests/TryCompile/CMakeLists.txt

@@ -89,6 +89,24 @@ if(SHOULD_FAIL)
    message(SEND_ERROR "Should fail passed ${TRY_OUT}")
 endif()
 
+# try to compile a file that should compile
+set(_c_flags "${CMAKE_C_FLAGS}")
+if(CMAKE_GENERATOR STREQUAL "Visual Studio 6")
+  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -D \"TESTDEF\"")
+elseif(WATCOM)
+  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -dTESTDEF")
+else()
+  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} \"-DTESTDEF\"")
+endif()
+try_compile(SHOULD_PASS
+    ${TryCompile_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp
+    ${TryCompile_SOURCE_DIR}/testdef.c
+    OUTPUT_VARIABLE TRY_OUT)
+if(NOT SHOULD_PASS)
+  message(SEND_ERROR "should pass failed ${TRY_OUT}")
+endif()
+set(CMAKE_C_FLAGS "${_c_flags}")
+
 if(NOT SHOULD_FAIL)
   if(SHOULD_PASS)
     message("All Tests passed, ignore all previous output.")

Tests/TryCompile/testdef.c

@@ -0,0 +1,4 @@
+#ifndef TESTDEF
+# error "TESTDEF should be defined!"
+#endif
+int main(void) { return 0; }