[Driver][Gnu] Support -nolibc flag

This can be used to disable libc linking. This flag is supported by
GCC since version 9 as well as some Clang target toolchains.

Differential Revision: https://reviews.llvm.org/D58326

llvm-svn: 354210

diff --git a/clang/lib/Driver/ToolChains/Gnu.cpp b/clang/lib/Driver/ToolChains/Gnu.cpp
index e94a895..6eb8fe2 100644 (file)
--- a/clang/lib/Driver/ToolChains/Gnu.cpp
+++ b/clang/lib/Driver/ToolChains/Gnu.cpp
@@ -518,7 +518,8 @@ void tools::gnutools::Linker::ConstructJob(Compilation &C, const JobAction &JA,
       if (Args.hasArg(options::OPT_fsplit_stack))
         CmdArgs.push_back("--wrap=pthread_create");
 
-      CmdArgs.push_back("-lc");
+      if (!Args.hasArg(options::OPT_nolibc))
+        CmdArgs.push_back("-lc");
 
       // Add IAMCU specific libs, if needed.
       if (IsIAMCU)

diff --git a/clang/test/Driver/nodefaultlib.c b/clang/test/Driver/nodefaultlib.c
index 08bcea5..e6c7d21 100644 (file)
--- a/clang/test/Driver/nodefaultlib.c
+++ b/clang/test/Driver/nodefaultlib.c
@@ -1,4 +1,4 @@
-// RUN: %clang -target i686-pc-linux-gnu -### -nodefaultlibs %s 2>&1 | FileCheck -check-prefix=TEST1 %s
+// RUN: %clang -target i686-pc-linux-gnu -### -rtlib=libgcc -nodefaultlibs %s 2>&1 | FileCheck -check-prefix=TEST1 %s
 // TEST1-NOT: start-group
 // TEST1-NOT: "-lgcc"
 // TEST1-NOT: "-lc"

diff --git a/clang/test/Driver/nolibc.c b/clang/test/Driver/nolibc.c
new file mode 100644 (file)
index 0000000..1fa1442
--- /dev/null
+++ b/clang/test/Driver/nolibc.c
@@ -0,0 +1,5 @@
+// RUN: %clang -target i686-pc-linux-gnu -### -rtlib=libgcc -nolibc %s 2>&1 | FileCheck %s
+// CHECK: crtbegin
+// CHECK: "-lgcc"
+// CHECK-NOT: "-lc"
+// CHECK: crtend