[Driver] add -lresolv for all but Android.

[kda]

Summary

As there 3 intercepts that depend on libresolv, link tests in ./configure scripts may be confuse by the presence of resolv symbols (i.e. dn_expand) even with -lresolv and get a runtime error.

Android provides the functionality in libc.

https://reviews.llvm.org/D122849
https://reviews.llvm.org/D126851

[MaskRay]

The description needs to mention the motivation. Is this meant for isOSLinux() && isGNUEnvironment() targets? Unless there is a case that sanitizer runtime uses libresolve.so while user code may not use -lresolv, this is not needed.

[vitalybuka]

yes, however I have no idea if we need !TC.getTriple().isOSFreeBSD() !TC.getTriple().isOSNetBSD() !TC.getTriple().isOSOpenBSD()) etc.
I guess if make mistake it will be noticed and fixed.

Please update clang/test/Driver/sanitizer-ld.c

[MaskRay]

clang/lib/Driver/ToolChains/CommonArgs.cpp

843

Omit brace for simple single-line body.

[eugenis]

The interceptor (dn_expand) is only defined on linux && !android, while this code links libresolv on *bsd and others, too. I think it's ok, as long as all platforms with the interceptor are covered.

It would be great to mention the actual reason we do this in the commit message: because otherwise link tests in ./configure scripts may be confused by the presence of the dn_expand symbol even without -lresolv (because of the interceptor) and get a runtime error later.

[kda]

In D127145#3561519, @eugenis wrote:

The interceptor (dn_expand) is only defined on linux && !android, while this code links libresolv on *bsd and others, too. I think it's ok, as long as all platforms with the interceptor are covered.

It would be great to mention the actual reason we do this in the commit message: because otherwise link tests in ./configure scripts may be confused by the presence of the dn_expand symbol even without -lresolv (because of the interceptor) and get a runtime error later.

Updated summary.

[eugenis]

Typo: "runttime"

LGTM

[kda]

removed braces on single statement from conditional

clang/lib/Driver/ToolChains/CommonArgs.cpp

if (!TC.getTriple().isOSFreeBSD() && !TC.getTriple().isOSNetBSD() &&
       !TC.getTriple().isOSOpenBSD() &&
       TC.getTriple().getOS() != llvm::Triple::RTEMS)
     CmdArgs.push_back("-ldl");
   // Required for backtrace on some OSes
   if (TC.getTriple().isOSFreeBSD() ||
       TC.getTriple().isOSNetBSD() ||
       TC.getTriple().isOSOpenBSD())
     CmdArgs.push_back("-lexecinfo");
+  // There is no libresolv on Android.
+  if (!TC.getTriple().isAndroid()) {
+    CmdArgs.push_back("-lresolv");
+  }
 }
 
 static void
 collectSanitizerRuntimes(const ToolChain &TC, const ArgList &Args,
                          SmallVectorImpl<StringRef> &SharedRuntimes,
                          SmallVectorImpl<StringRef> &StaticRuntimes,
                          SmallVectorImpl<StringRef> &NonWholeStaticRuntimes,
                          SmallVectorImpl<StringRef> &HelperStaticRuntimes,

compiler-rt/test/msan/Linux/b64.cpp

-// RUN: %clangxx_msan -O0 %s -o %t -lresolv && %run %t
+// RUN: %clangxx_msan -O0 %s -o %t && %run %t
 // RUN: not %run %t NTOP_READ 2>&1 | FileCheck %s --check-prefix=NTOP_READ
 // RUN: not %run %t PTON_READ 2>&1 | FileCheck %s --check-prefix=PTON_READ
 
 #include <assert.h>
 #include <resolv.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/types.h>

compiler-rt/test/msan/Linux/dn_expand.cpp

-// RUN: %clangxx_msan -O0 %s -o %t -lresolv && %run %t
+// RUN: %clangxx_msan -O0 %s -o %t && %run %t
 
 #include <assert.h>
 #include <resolv.h>
 #include <string.h>
 
 #include <sanitizer/msan_interface.h>
 
 void testWrite() {

compiler-rt/test/sanitizer_common/TestCases/Linux/b64.cpp

-// RUN: %clangxx %s -o %t -lresolv && %run %t %p
-
-// -lresolv fails on Android.
-// UNSUPPORTED: android
+// RUN: %clangxx %s -o %t && %run %t %p
 
 #include <assert.h>
 #include <resolv.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/types.h>
 
 int main(int iArgc, char *szArgv[]) {

compiler-rt/test/sanitizer_common/TestCases/Linux/dn_expand.cpp

-// RUN: %clangxx %s -o %t -lresolv && %run %t %p
-
-// -lresolv fails on Android.
-// UNSUPPORTED: android
+// RUN: %clangxx %s -o %t && %run %t %p
 
 #include <assert.h>
 #include <resolv.h>
 #include <string.h>
 
 #include <sanitizer/msan_interface.h>
 
 void testWrite() {