[lldb] [test] Skip Expr/nodefaultlib.cpp test if LD_PRELOAD Is used

[mgorny]

Summary

Some LD_PRELOAD-ed libraries tend to interact badly with --nodefaultlib,
particularly Gentoo sandbox. Do not run this test if LD_PRELOAD is
present in the running environment.

[JDevlieghere]

LGTM

[mgorny]

Thanks!

[labath]

What does the preloaded library do ? Is it actually necessary for the (other) tests to run? I'm wondering if we shouldn't strip the variable from the environment instead...

[mgorny]

In D107701#2986378, @labath wrote:

What does the preloaded library do ? Is it actually necessary for the (other) tests to run? I'm wondering if we shouldn't strip the variable from the environment instead...

It detects accesses to files outside the build tree. Stripping the variable won't help because it will readd itself on fork.

lldb/test/Shell/Expr/nodefaultlib.cpp

 // Test that we're able to evaluate expressions in inferiors without the
 // standard library (and mmap-like functions in particular).
 
 // REQUIRES: native
+// UNSUPPORTED: ld_preload-present
 // XFAIL: system-linux && !(target-x86 || target-x86_64)
 // XFAIL: system-netbsd || system-freebsd || system-darwin
 
 // RUN: %build %s --nodefaultlib -o %t
 // RUN: %lldb %t -o "b main" -o run -o "p call_me(5, 6)" -o exit \
 // RUN:   | FileCheck %s
 
 // CHECK: p call_me(5, 6)
 // CHECK: (int) $0 = 30
 
 int call_me(int x, long y) { return x * y; }
 
 int main() { return call_me(4, 5); }

lldb/test/Shell/lit.cfg.py

try:
         output = subprocess.check_output(["/sbin/sysctl", "-n",
           "security.models.extensions.user_set_dbregs"]).decode().strip()
         if output != "1":
             can_set_dbregs = False
     except subprocess.CalledProcessError:
         can_set_dbregs = False
 if can_set_dbregs:
     config.available_features.add('dbregs-set')
+
+if 'LD_PRELOAD' in os.environ:
+    config.available_features.add('ld_preload-present')