issue-5041: do not add extra flags when compiler or platform does not support them (#5042)

* check for suitable compiler (platform) before adding special flags

* pep8 corrections

* later pep8 messages

* add clang to auto accepted compilers

* modify syntax so multi-line is accepted

1 files changed, 13 insertions, 1 deletions

diff --git a/src/_cffi_src/build_openssl.py b/src/_cffi_src/build_openssl.py
index d3d27df6..1740cc59 100644
--- a/src/_cffi_src/build_openssl.py
+++ b/src/_cffi_src/build_openssl.py
@@ -6,6 +6,9 @@ from __future__ import absolute_import, division, print_function
 
 import os
 import sys
+from distutils import dist
+from distutils.ccompiler import get_default_compiler
+from distutils.command.config import config
 
 from _cffi_src.utils import (
     build_ffi_for_binding, compiler_type, extra_link_args
@@ -47,7 +50,16 @@ def _extra_compile_args(platform):
     When we drop support for CRYPTOGRAPHY_OPENSSL_LESS_THAN_110 we can
     revisit this.
     """
-    if platform not in ["win32", "hp-ux11", "sunos5"]:
+    # make sure the compiler used supports the flags to be added
+    is_gcc = False
+    if get_default_compiler() == "unix":
+        d = dist.Distribution()
+        cmd = config(d)
+        cmd._check_compiler()
+        is_gcc = ("gcc" in cmd.compiler.compiler[0] or
+                  "clang" in cmd.compiler.compiler[0])
+    if is_gcc or not (platform in ["win32", "hp-ux11", "sunos5"] or
+                      platform.startswith("aix")):
         return ["-Wconversion", "-Wno-error=sign-conversion"]
     else:
         return []