[PATCH] perf python: better clang detection

[Ilie Halip]

Currently, the setup.py script detects the clang compiler only when invoked
with CC=clang. But when using a specific version (e.g. CC=clang-11), this
doesn't work correctly and wrong compiler flags are set, leading to build
errors.

To properly detect clang, invoke the compiler with -v and check the output.
The first line should start with "clang version ...".

Link: https://github.com/ClangBuiltLinux/linux/issues/903
Signed-off-by: Ilie Halip <ilie.halip@xxxxxxxxx>
---
 tools/perf/util/setup.py | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/setup.py b/tools/perf/util/setup.py
index aa344a163eaf..8a065a6f9713 100644
--- a/tools/perf/util/setup.py
+++ b/tools/perf/util/setup.py
@@ -2,11 +2,13 @@ from os import getenv
 from subprocess import Popen, PIPE
 from re import sub
 
+cc = getenv("CC")
+cc_is_clang = b"clang version" in Popen([cc, "-v"], stderr=PIPE).stderr.readline()
+
 def clang_has_option(option):
-    return [o for o in Popen(['clang', option], stderr=PIPE).stderr.readlines() if b"unknown argument" in o] == [ ]
+    return [o for o in Popen([cc, option], stderr=PIPE).stderr.readlines() if b"unknown argument" in o] == [ ]
 
-cc = getenv("CC")
-if cc == "clang":
+if cc_is_clang:
     from distutils.sysconfig import get_config_vars
     vars = get_config_vars()
     for var in ('CFLAGS', 'OPT'):
@@ -40,7 +42,7 @@ class install_lib(_install_lib):
 cflags = getenv('CFLAGS', '').split()
 # switch off several checks (need to be at the end of cflags list)
 cflags += ['-fno-strict-aliasing', '-Wno-write-strings', '-Wno-unused-parameter', '-Wno-redundant-decls' ]
-if cc != "clang":
+if not cc_is_clang:
     cflags += ['-Wno-cast-function-type' ]
 
 src_perf  = getenv('srctree') + '/tools/perf'
-- 
2.17.1