8327701: Remove the xlc toolchain

Reviewed-by: jwaters, erikj

Author: magicus

doc/building.html

@@ -68,7 +68,8 @@ <h1 class="title">Building the JDK</h1>
 <li><a href="#apple-xcode" id="toc-apple-xcode">Apple Xcode</a></li>
 <li><a href="#microsoft-visual-studio"
 id="toc-microsoft-visual-studio">Microsoft Visual Studio</a></li>
-<li><a href="#ibm-xl-cc" id="toc-ibm-xl-cc">IBM XL C/C++</a></li>
+<li><a href="#ibm-open-xl-cc" id="toc-ibm-open-xl-cc">IBM Open XL
+C/C++</a></li>
 </ul></li>
 <li><a href="#boot-jdk-requirements" id="toc-boot-jdk-requirements">Boot
 JDK Requirements</a>
@@ -673,11 +674,10 @@ <h3 id="microsoft-visual-studio">Microsoft Visual Studio</h3>
 version number accordingly. If you have not installed the
 <code>BuildTools</code>, but e.g. <code>Professional</code>, adjust the
 product ID accordingly.</p>
-<h3 id="ibm-xl-cc">IBM XL C/C++</h3>
-<p>Please consult the AIX section of the <a
-href="https://wiki.openjdk.org/display/Build/Supported+Build+Platforms">Supported
-Build Platforms</a> OpenJDK Build Wiki page for details about which
-versions of XLC are supported.</p>
+<h3 id="ibm-open-xl-cc">IBM Open XL C/C++</h3>
+<p>The minimum accepted version of Open XL is 17.1.1.4. This is in
+essence clang 15, and will be treated as such by the OpenJDK build
+system.</p>
 <h2 id="boot-jdk-requirements">Boot JDK Requirements</h2>
 <p>Paradoxically, building the JDK requires a pre-existing JDK. This is
 called the "boot JDK". The boot JDK does not, however, have to be a JDK

doc/building.md

@@ -487,11 +487,10 @@ that the " characters are essential)
 accordingly. If you have not installed the `BuildTools`, but e.g.
 `Professional`, adjust the product ID accordingly.
 
-### IBM XL C/C++
+### IBM Open XL C/C++
 
-Please consult the AIX section of the [Supported Build Platforms](
-https://wiki.openjdk.org/display/Build/Supported+Build+Platforms) OpenJDK Build
-Wiki page for details about which versions of XLC are supported.
+The minimum accepted version of Open XL is 17.1.1.4. This is in essence clang
+15, and will be treated as such by the OpenJDK build system.
 
 ## Boot JDK Requirements
 

make/autoconf/build-performance.m4

@@ -1,5 +1,5 @@
 #
-# Copyright (c) 2011, 2023, Oracle and/or its affiliates. All rights reserved.
+# Copyright (c) 2011, 2024, Oracle and/or its affiliates. All rights reserved.
 # DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 #
 # This code is free software; you can redistribute it and/or modify it
@@ -359,9 +359,6 @@ AC_DEFUN_ONCE([BPERF_SETUP_PRECOMPILED_HEADERS],
   if test "x$ICECC" != "x"; then
     AC_MSG_RESULT([no, does not work effectively with icecc])
     PRECOMPILED_HEADERS_AVAILABLE=false
-  elif test "x$TOOLCHAIN_TYPE" = xxlc; then
-    AC_MSG_RESULT([no, does not work with xlc])
-    PRECOMPILED_HEADERS_AVAILABLE=false
   elif test "x$TOOLCHAIN_TYPE" = xgcc; then
     # Check that the compiler actually supports precomp headers.
     echo "int alfa();" > conftest.h

make/autoconf/flags-cflags.m4

@@ -77,12 +77,6 @@ AC_DEFUN([FLAGS_SETUP_SHARED_LIBS],
       fi
     fi
 
-  elif test "x$TOOLCHAIN_TYPE" = xxlc; then
-    SHARED_LIBRARY_FLAGS="-qmkshrobj -bM:SRE -bnoentry"
-    SET_EXECUTABLE_ORIGIN=""
-    SET_SHARED_LIBRARY_ORIGIN=''
-    SET_SHARED_LIBRARY_NAME=''
-
   elif test "x$TOOLCHAIN_TYPE" = xmicrosoft; then
     SHARED_LIBRARY_FLAGS="-dll"
     SET_EXECUTABLE_ORIGIN=''
@@ -152,8 +146,6 @@ AC_DEFUN([FLAGS_SETUP_DEBUG_SYMBOLS],
 
     CFLAGS_DEBUG_SYMBOLS="-g ${GDWARF_FLAGS}"
     ASFLAGS_DEBUG_SYMBOLS="-g"
-  elif test "x$TOOLCHAIN_TYPE" = xxlc; then
-    CFLAGS_DEBUG_SYMBOLS="-g1"
   elif test "x$TOOLCHAIN_TYPE" = xmicrosoft; then
     CFLAGS_DEBUG_SYMBOLS="-Z7"
   fi
@@ -219,11 +211,7 @@ AC_DEFUN([DEBUG_PREFIX_MAP_GCC_INCLUDE_PATHS],
 AC_DEFUN([FLAGS_SETUP_WARNINGS],
 [
   # Set default value.
-  if test "x$TOOLCHAIN_TYPE" != xxlc; then
-    WARNINGS_AS_ERRORS_DEFAULT=true
-  else
-    WARNINGS_AS_ERRORS_DEFAULT=false
-  fi
+  WARNINGS_AS_ERRORS_DEFAULT=true
 
   UTIL_ARG_ENABLE(NAME: warnings-as-errors, DEFAULT: $WARNINGS_AS_ERRORS_DEFAULT,
       RESULT: WARNINGS_AS_ERRORS,
@@ -273,15 +261,6 @@ AC_DEFUN([FLAGS_SETUP_WARNINGS],
 
       DISABLED_WARNINGS="unknown-warning-option unused-parameter unused"
       ;;
-
-    xlc)
-      DISABLE_WARNING_PREFIX="-Wno-"
-      CFLAGS_WARNINGS_ARE_ERRORS="-qhalt=w"
-
-      # Possibly a better subset than "all" is "lan:trx:ret:zea:cmp:ret"
-      WARNINGS_ENABLE_ALL="-qinfo=all -qformat=all"
-      DISABLED_WARNINGS=""
-      ;;
   esac
   AC_SUBST(DISABLE_WARNING_PREFIX)
   AC_SUBST(BUILD_CC_DISABLE_WARNING_PREFIX)
@@ -363,15 +342,6 @@ AC_DEFUN([FLAGS_SETUP_OPTIMIZATION],
     C_O_FLAG_SIZE="-Os"
     C_O_FLAG_DEBUG="-O0"
     C_O_FLAG_NONE="-O0"
-  elif test "x$TOOLCHAIN_TYPE" = xxlc; then
-    C_O_FLAG_HIGHEST_JVM="-O3 -qhot=level=1 -qinline -qinlglue"
-    C_O_FLAG_HIGHEST="-O3 -qhot=level=1 -qinline -qinlglue"
-    C_O_FLAG_HI="-O3 -qinline -qinlglue"
-    C_O_FLAG_NORM="-O2"
-    C_O_FLAG_DEBUG="-qnoopt"
-    # FIXME: Value below not verified.
-    C_O_FLAG_DEBUG_JVM=""
-    C_O_FLAG_NONE="-qnoopt"
   elif test "x$TOOLCHAIN_TYPE" = xmicrosoft; then
     C_O_FLAG_HIGHEST_JVM="-O2 -Oy-"
     C_O_FLAG_HIGHEST="-O2"
@@ -524,12 +494,6 @@ AC_DEFUN([FLAGS_SETUP_CFLAGS_HELPER],
   else
     DEBUG_CFLAGS_JDK="-DDEBUG"
 
-    if test "x$TOOLCHAIN_TYPE" = xxlc; then
-      # We need '-qminimaltoc' or '-qpic=large -bbigtoc' if the TOC overflows.
-      # Hotspot now overflows its 64K TOC (currently only for debug),
-      # so for debug we build with '-qpic=large -bbigtoc'.
-      DEBUG_CFLAGS_JVM="-qpic=large"
-    fi
     if test "x$TOOLCHAIN_TYPE" = xclang && test "x$OPENJDK_TARGET_OS" = xaix; then
       DEBUG_CFLAGS_JVM="-fpic -mcmodel=large"
     fi
@@ -546,9 +510,6 @@ AC_DEFUN([FLAGS_SETUP_CFLAGS_HELPER],
     ALWAYS_DEFINES_JVM="-D_GNU_SOURCE -D_REENTRANT"
   elif test "x$TOOLCHAIN_TYPE" = xclang; then
     ALWAYS_DEFINES_JVM="-D_GNU_SOURCE"
-  elif test "x$TOOLCHAIN_TYPE" = xxlc; then
-    ALWAYS_DEFINES_JVM="-D_REENTRANT"
-    ALWAYS_DEFINES_JDK="-D_GNU_SOURCE -D_REENTRANT -DSTDC"
   elif test "x$TOOLCHAIN_TYPE" = xmicrosoft; then
     # Access APIs for Windows 8 and above
     # see https://docs.microsoft.com/en-us/cpp/porting/modifying-winver-and-win32-winnt?view=msvc-170
@@ -612,12 +573,6 @@ AC_DEFUN([FLAGS_SETUP_CFLAGS_HELPER],
       TOOLCHAIN_CFLAGS_JDK_CONLY="-fno-strict-aliasing" # technically NOT for CXX
     fi
 
-  elif test "x$TOOLCHAIN_TYPE" = xxlc; then
-    # Suggested additions: -qsrcmsg to get improved error reporting
-    # set -qtbtable=full for a better traceback table/better stacks in hs_err when xlc16 is used
-    TOOLCHAIN_CFLAGS_JDK="-qtbtable=full -qchars=signed -qfullpath -qsaveopt -qstackprotect"  # add on both CFLAGS
-    TOOLCHAIN_CFLAGS_JVM="-qtbtable=full -qtune=balanced -fno-exceptions \
-        -qalias=noansi -qstrict -qtls=default -qnortti -qnoeh -qignerrno -qstackprotect"
   elif test "x$TOOLCHAIN_TYPE" = xmicrosoft; then
     # The -utf-8 option sets source and execution character sets to UTF-8 to enable correct
     # compilation of all source files regardless of the active code page on Windows.
@@ -626,20 +581,20 @@ AC_DEFUN([FLAGS_SETUP_CFLAGS_HELPER],
   fi
 
   # CFLAGS C language level for JDK sources (hotspot only uses C++)
-  if test "x$TOOLCHAIN_TYPE" = xgcc || test "x$TOOLCHAIN_TYPE" = xclang || test "x$TOOLCHAIN_TYPE" = xxlc; then
+  if test "x$TOOLCHAIN_TYPE" = xgcc || test "x$TOOLCHAIN_TYPE" = xclang; then
     LANGSTD_CFLAGS="-std=c11"
   elif test "x$TOOLCHAIN_TYPE" = xmicrosoft; then
     LANGSTD_CFLAGS="-std:c11"
   fi
   TOOLCHAIN_CFLAGS_JDK_CONLY="$LANGSTD_CFLAGS $TOOLCHAIN_CFLAGS_JDK_CONLY"
 
   # CXXFLAGS C++ language level for all of JDK, including Hotspot.
-  if test "x$TOOLCHAIN_TYPE" = xgcc || test "x$TOOLCHAIN_TYPE" = xclang || test "x$TOOLCHAIN_TYPE" = xxlc; then
+  if test "x$TOOLCHAIN_TYPE" = xgcc || test "x$TOOLCHAIN_TYPE" = xclang; then
     LANGSTD_CXXFLAGS="-std=c++14"
   elif test "x$TOOLCHAIN_TYPE" = xmicrosoft; then
     LANGSTD_CXXFLAGS="-std:c++14"
   else
-    AC_MSG_ERROR([Don't know how to enable C++14 for this toolchain])
+    AC_MSG_ERROR([Cannot enable C++14 for this toolchain])
   fi
   TOOLCHAIN_CFLAGS_JDK_CXXONLY="$TOOLCHAIN_CFLAGS_JDK_CXXONLY $LANGSTD_CXXFLAGS"
   TOOLCHAIN_CFLAGS_JVM="$TOOLCHAIN_CFLAGS_JVM $LANGSTD_CXXFLAGS"
@@ -658,8 +613,6 @@ AC_DEFUN([FLAGS_SETUP_CFLAGS_HELPER],
   elif test "x$TOOLCHAIN_TYPE" = xmicrosoft; then
     WARNING_CFLAGS="$WARNINGS_ENABLE_ALL"
 
-  elif test "x$TOOLCHAIN_TYPE" = xxlc; then
-    WARNING_CFLAGS=""  # currently left empty
   fi
 
   # Set some additional per-OS defines.
@@ -684,31 +637,16 @@ AC_DEFUN([FLAGS_SETUP_CFLAGS_HELPER],
   if test "x$TOOLCHAIN_TYPE" = xgcc || test "x$TOOLCHAIN_TYPE" = xclang; then
     PICFLAG="-fPIC"
     PIEFLAG="-fPIE"
-  elif test "x$TOOLCHAIN_TYPE" = xclang && test "x$OPENJDK_TARGET_OS" = xaix; then
-    JVM_PICFLAG="-fpic -mcmodel=large -Wl,-bbigtoc
-    JDK_PICFLAG="-fpic
-  elif test "x$TOOLCHAIN_TYPE" = xxlc; then
-    # '-qpic' defaults to 'qpic=small'. This means that the compiler generates only
-    # one instruction for accessing the TOC. If the TOC grows larger than 64K, the linker
-    # will have to patch this single instruction with a call to some out-of-order code which
-    # does the load from the TOC. This is of course slower, and we also would have
-    # to use '-bbigtoc' for linking anyway so we could also change the PICFLAG to 'qpic=large'.
-    # With 'qpic=large' the compiler will by default generate a two-instruction sequence which
-    # can be patched directly by the linker and does not require a jump to out-of-order code.
-    #
-    # Since large TOC causes perf. overhead, only pay it where we must. Currently this is
-    # for all libjvm variants (both gtest and normal) but no other binaries. So, build
-    # libjvm with -qpic=large and link with -bbigtoc.
-    JVM_PICFLAG="-qpic=large"
-    JDK_PICFLAG="-qpic"
   elif test "x$TOOLCHAIN_TYPE" = xmicrosoft; then
     PICFLAG=""
   fi
 
-  if test "x$TOOLCHAIN_TYPE" != xxlc; then
+  if test "x$TOOLCHAIN_TYPE" = xclang && test "x$OPENJDK_TARGET_OS" = xaix; then
+    JVM_PICFLAG="-fpic -mcmodel=large"
+  else
     JVM_PICFLAG="$PICFLAG"
-    JDK_PICFLAG="$PICFLAG"
   fi
+  JDK_PICFLAG="$PICFLAG"
 
   if test "x$OPENJDK_TARGET_OS" = xmacosx; then
     # Linking is different on MacOSX
@@ -758,8 +696,7 @@ AC_DEFUN([FLAGS_SETUP_CFLAGS_CPU_DEP],
   $1_DEFINES_CPU_JDK="${$1_DEFINES_CPU_JDK} -DARCH='\"$FLAGS_CPU_LEGACY\"' \
       -D$FLAGS_CPU_LEGACY"
 
-  if test "x$FLAGS_CPU_BITS" = x64 && test "x$FLAGS_OS" != xaix; then
-    # xlc on AIX defines _LP64=1 by default and issues a warning if we redefine it.
+  if test "x$FLAGS_CPU_BITS" = x64; then
     $1_DEFINES_CPU_JDK="${$1_DEFINES_CPU_JDK} -D_LP64=1"
     $1_DEFINES_CPU_JVM="${$1_DEFINES_CPU_JVM} -D_LP64=1"
   fi
@@ -836,11 +773,6 @@ AC_DEFUN([FLAGS_SETUP_CFLAGS_CPU_DEP],
       $1_CFLAGS_CPU="-mcpu=pwr8"
     fi
 
-  elif test "x$TOOLCHAIN_TYPE" = xxlc; then
-    if test "x$FLAGS_CPU" = xppc64; then
-      $1_CFLAGS_CPU_JVM="-qarch=ppc64"
-    fi
-
   elif test "x$TOOLCHAIN_TYPE" = xmicrosoft; then
     if test "x$FLAGS_CPU" = xx86; then
       $1_CFLAGS_CPU_JVM="-arch:IA32"

make/autoconf/flags-ldflags.m4

@@ -86,11 +86,6 @@ AC_DEFUN([FLAGS_SETUP_LDFLAGS_HELPER],
         -Wl,-bernotok -Wl,-bdatapsize:64k -Wl,-btextpsize:64k -Wl,-bstackpsize:64k"
       BASIC_LDFLAGS_JVM_ONLY="$BASIC_LDFLAGS_JVM_ONLY -Wl,-lC_r -Wl,-bbigtoc"
     fi
-  elif test "x$TOOLCHAIN_TYPE" = xxlc; then
-    BASIC_LDFLAGS="-b64 -brtl -bnorwexec -bnolibpath -bnoexpall -bernotok -btextpsize:64K \
-        -bdatapsize:64K -bstackpsize:64K"
-    # libjvm.so has gotten too large for normal TOC size; compile with qpic=large and link with bigtoc
-    BASIC_LDFLAGS_JVM_ONLY="-Wl,-lC_r -bbigtoc"
 
   elif test "x$TOOLCHAIN_TYPE" = xmicrosoft; then
     BASIC_LDFLAGS="-opt:ref"
@@ -120,14 +115,6 @@ AC_DEFUN([FLAGS_SETUP_LDFLAGS_HELPER],
       fi
     fi
 
-  elif test "x$TOOLCHAIN_TYPE" = xxlc; then
-    # We need '-qminimaltoc' or '-qpic=large -bbigtoc' if the TOC overflows.
-    # Hotspot now overflows its 64K TOC (currently only for debug),
-    # so we build with '-qpic=large -bbigtoc'.
-    if test "x$DEBUG_LEVEL" != xrelease; then
-      DEBUGLEVEL_LDFLAGS_JVM_ONLY="$DEBUGLEVEL_LDFLAGS_JVM_ONLY -bbigtoc"
-    fi
-
   elif test "x$TOOLCHAIN_TYPE" = xclang && test "x$OPENJDK_TARGET_OS" = xaix; then
     # We need '-fpic' or '-fpic -mcmodel=large -Wl,-bbigtoc' if the TOC overflows.
     # Hotspot now overflows its 64K TOC (currently only for debug),

make/autoconf/flags.m4

@@ -261,12 +261,9 @@ AC_DEFUN_ONCE([FLAGS_PRE_TOOLCHAIN],
   # The sysroot flags are needed for configure to be able to run the compilers
   FLAGS_SETUP_SYSROOT_FLAGS
 
-  # For xlc, the word size flag is required for correct behavior.
   # For clang/gcc, the flag is only strictly required for reduced builds, but
   # set it always where possible (x86 and ppc).
-  if test "x$TOOLCHAIN_TYPE" = xxlc; then
-    MACHINE_FLAG="-q${OPENJDK_TARGET_CPU_BITS}"
-  elif test "x$TOOLCHAIN_TYPE" = xgcc || test "x$TOOLCHAIN_TYPE" = xclang; then
+  if test "x$TOOLCHAIN_TYPE" = xgcc || test "x$TOOLCHAIN_TYPE" = xclang; then
     if test "x$OPENJDK_TARGET_CPU_ARCH" = xx86 &&
         test "x$OPENJDK_TARGET_CPU" != xx32 ||
         test "x$OPENJDK_TARGET_CPU_ARCH" = xppc; then
@@ -321,47 +318,6 @@ AC_DEFUN_ONCE([FLAGS_PRE_TOOLCHAIN],
 
 AC_DEFUN([FLAGS_SETUP_TOOLCHAIN_CONTROL],
 [
-  # COMPILER_TARGET_BITS_FLAG  : option for selecting 32- or 64-bit output
-  # COMPILER_COMMAND_FILE_FLAG : option for passing a command file to the compiler
-  # COMPILER_BINDCMD_FILE_FLAG : option for specifying a file which saves the binder
-  #                              commands produced by the link step (currently AIX only)
-  if test "x$TOOLCHAIN_TYPE" = xxlc; then
-    COMPILER_TARGET_BITS_FLAG="-q"
-    COMPILER_COMMAND_FILE_FLAG="-f"
-    COMPILER_BINDCMD_FILE_FLAG="-bloadmap:"
-  else
-    COMPILER_TARGET_BITS_FLAG="-m"
-    COMPILER_COMMAND_FILE_FLAG="@"
-    COMPILER_BINDCMD_FILE_FLAG=""
-
-    # Check if @file is supported by gcc
-    if test "x$TOOLCHAIN_TYPE" = xgcc; then
-      AC_MSG_CHECKING([if @file is supported by gcc])
-      # Extra empty "" to prevent ECHO from interpreting '--version' as argument
-      $ECHO "" "--version" > command.file
-      # Redirect stderr and stdout to config.log (AS_MESSAGE_LOG_FD) via merge
-      if $CXX @command.file 2>&AS_MESSAGE_LOG_FD >&AS_MESSAGE_LOG_FD; then
-        AC_MSG_RESULT(yes)
-        COMPILER_COMMAND_FILE_FLAG="@"
-      else
-        AC_MSG_RESULT(no)
-        COMPILER_COMMAND_FILE_FLAG=
-      fi
-      $RM command.file
-    fi
-  fi
-
-  AC_SUBST(COMPILER_TARGET_BITS_FLAG)
-  AC_SUBST(COMPILER_COMMAND_FILE_FLAG)
-  AC_SUBST(COMPILER_BINDCMD_FILE_FLAG)
-
-  # Check that the compiler supports -mX (or -qX on AIX) flags
-  # Set COMPILER_SUPPORTS_TARGET_BITS_FLAG to 'true' if it does
-  FLAGS_COMPILER_CHECK_ARGUMENTS(ARGUMENT: [${COMPILER_TARGET_BITS_FLAG}${OPENJDK_TARGET_CPU_BITS}],
-      IF_TRUE: [COMPILER_SUPPORTS_TARGET_BITS_FLAG=true],
-      IF_FALSE: [COMPILER_SUPPORTS_TARGET_BITS_FLAG=false])
-  AC_SUBST(COMPILER_SUPPORTS_TARGET_BITS_FLAG)
-
   if test "x$TOOLCHAIN_TYPE" = xmicrosoft; then
     CC_OUT_OPTION=-Fo
   else
@@ -376,8 +332,6 @@ AC_DEFUN([FLAGS_SETUP_TOOLCHAIN_CONTROL],
     GENDEPS_FLAGS="-MMD -MF"
   elif test "x$TOOLCHAIN_TYPE" = xclang; then
     GENDEPS_FLAGS="-MMD -MF"
-  elif test "x$TOOLCHAIN_TYPE" = xxlc; then
-    GENDEPS_FLAGS="-qmakedep=gcc -MF"
   fi
   AC_SUBST(GENDEPS_FLAGS)
 ])

make/autoconf/spec.gmk.template

@@ -477,7 +477,7 @@ MACOSX_VERSION_MAX := @MACOSX_VERSION_MAX@
 MACOSX_CODESIGN_MODE := @MACOSX_CODESIGN_MODE@
 MACOSX_CODESIGN_IDENTITY := @MACOSX_CODESIGN_IDENTITY@
 
-# Toolchain type: gcc, clang, xlc, microsoft...
+# Toolchain type: gcc, clang, microsoft...
 TOOLCHAIN_TYPE := @TOOLCHAIN_TYPE@
 TOOLCHAIN_VERSION := @TOOLCHAIN_VERSION@
 CC_VERSION_NUMBER := @CC_VERSION_NUMBER@
@@ -486,17 +486,6 @@ CXX_VERSION_NUMBER := @CXX_VERSION_NUMBER@
 # Legacy support
 HOTSPOT_TOOLCHAIN_TYPE := @HOTSPOT_TOOLCHAIN_TYPE@
 
-# Option used to tell the compiler whether to create 32- or 64-bit executables
-COMPILER_TARGET_BITS_FLAG := @COMPILER_TARGET_BITS_FLAG@
-COMPILER_SUPPORTS_TARGET_BITS_FLAG := @COMPILER_SUPPORTS_TARGET_BITS_FLAG@
-
-# Option used to pass a command file to the compiler
-COMPILER_COMMAND_FILE_FLAG := @COMPILER_COMMAND_FILE_FLAG@
-
-# Option for specifying a file which saves the binder commands
-# produced by the link step (for debugging, currently AIX only)
-COMPILER_BINDCMD_FILE_FLAG := @COMPILER_BINDCMD_FILE_FLAG@
-
 CC_OUT_OPTION := @CC_OUT_OPTION@
 
 # Flags used for overriding the default opt setting for a C/C++ source file.