[PATCH v3 4/7] BaseTools/tools_def CLANG3x ARM AARCH64: force use of C99 standard

["Ard Biesheuvel" <ard.biesheuvel@linaro.org>]

When building OpenSSL for ARM or AARCH64 with recent Clang, the following
error may result:

  In file included from .../CryptoPkg/Library/BaseCryptLib/Pk/CryptPkcs7VerifyEku.c:18:
  In file included from .../CryptoPkg/Library/OpensslLib/openssl/crypto/include/internal/x509_int.h:10:
  In file included from .../CryptoPkg/Library/OpensslLib/openssl/include/internal/refcount.h:21:
  In file included from /usr/lib/llvm-7/lib/clang/7.0.1/include/stdatomic.h:35:
  In file included from /usr/lib/llvm-7/lib/clang/7.0.1/include/stdint.h:61:
  /usr/include/stdint.h:26:10: fatal error: 'bits/libc-header-start.h' file not found
  #include <bits/libc-header-start.h>
         ^~~~~~~~~~~~~~~~~~~~~~~~~~
  1 error generated.

This is caused by the fact that the refcount.h header includes compiler
headers that in turn rely on system headers, which we don't support.

Since the C native atomics are a C11 feature, let's explicitly use the
C99 standard instead to work around this issue, and add the -ffreestanding
option so that the compiler never attempts to include system headers.

Acked-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 BaseTools/Conf/tools_def.template | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/BaseTools/Conf/tools_def.template b/BaseTools/Conf/tools_def.template
index 26a2cf604f74..f1467d5e8cef 100755
--- a/BaseTools/Conf/tools_def.template
+++ b/BaseTools/Conf/tools_def.template
@@ -2280,8 +2280,8 @@ DEFINE CLANG35_ARM_TARGET        = -target arm-linux-gnueabi
 DEFINE CLANG35_AARCH64_TARGET    = -target aarch64-linux-gnu
 
 DEFINE CLANG35_WARNING_OVERRIDES = -Wno-parentheses-equality -Wno-tautological-compare -Wno-tautological-constant-out-of-range-compare -Wno-empty-body -Wno-unknown-warning-option
-DEFINE CLANG35_ARM_CC_FLAGS      = DEF(GCC_ARM_CC_FLAGS) DEF(CLANG35_ARM_TARGET) DEF(CLANG35_WARNING_OVERRIDES)
-DEFINE CLANG35_AARCH64_CC_FLAGS  = DEF(GCC_AARCH64_CC_FLAGS) DEF(CLANG35_AARCH64_TARGET) -mcmodel=small DEF(CLANG35_WARNING_OVERRIDES)
+DEFINE CLANG35_ARM_CC_FLAGS      = DEF(GCC_ARM_CC_FLAGS) DEF(CLANG35_ARM_TARGET) DEF(CLANG35_WARNING_OVERRIDES) -std=c99 -ffreestanding
+DEFINE CLANG35_AARCH64_CC_FLAGS  = DEF(GCC_AARCH64_CC_FLAGS) DEF(CLANG35_AARCH64_TARGET) -mcmodel=small DEF(CLANG35_WARNING_OVERRIDES) -std=c99 -ffreestanding
 
 ##################
 # CLANG35 ARM definitions
@@ -2430,7 +2430,7 @@ NOOPT_CLANG38_X64_DLINK2_FLAGS     = DEF(GCC5_X64_DLINK2_FLAGS) -O0
 # CLANG38 ARM definitions
 ##################
 DEFINE CLANG38_ARM_TARGET        = -target arm-linux-gnueabi
-DEFINE CLANG38_ARM_CC_FLAGS      = DEF(GCC_ARM_CC_FLAGS) DEF(CLANG38_ARM_TARGET) DEF(CLANG38_WARNING_OVERRIDES) -mno-movt
+DEFINE CLANG38_ARM_CC_FLAGS      = DEF(GCC_ARM_CC_FLAGS) DEF(CLANG38_ARM_TARGET) DEF(CLANG38_WARNING_OVERRIDES) -mno-movt -std=c99 -ffreestanding
 DEFINE CLANG38_ARM_DLINK_FLAGS   = DEF(CLANG38_ARM_TARGET) DEF(GCC_ARM_DLINK_FLAGS)
 
 *_CLANG38_ARM_PP_FLAGS           = DEF(GCC_PP_FLAGS)
@@ -2474,7 +2474,7 @@ RELEASE_CLANG38_ARM_DLINK_FLAGS  = DEF(CLANG38_ARM_DLINK_FLAGS) -flto -Wl,-O3 -L
 # CLANG38 AARCH64 definitions
 ##################
 DEFINE CLANG38_AARCH64_TARGET    = -target aarch64-linux-gnu
-DEFINE CLANG38_AARCH64_CC_FLAGS  = DEF(GCC_AARCH64_CC_FLAGS) DEF(CLANG38_AARCH64_TARGET) -mcmodel=small DEF(CLANG38_WARNING_OVERRIDES)
+DEFINE CLANG38_AARCH64_CC_FLAGS  = DEF(GCC_AARCH64_CC_FLAGS) DEF(CLANG38_AARCH64_TARGET) -mcmodel=small DEF(CLANG38_WARNING_OVERRIDES) -std=c99 -ffreestanding
 DEFINE CLANG38_AARCH64_DLINK_FLAGS  = DEF(CLANG38_AARCH64_TARGET) DEF(GCC_AARCH64_DLINK_FLAGS) -z common-page-size=0x1000
 
 *_CLANG38_AARCH64_PP_FLAGS       = DEF(GCC_PP_FLAGS)
-- 
2.20.1