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[flang][Driver] Support -nostdlib and -nodefaultlibs #108868

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Sep 17, 2024
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[flang][Driver] Support -nostdlib and -nodefaultlibs #108868

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7 changes: 5 additions & 2 deletions clang/include/clang/Driver/Options.td
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Expand Up @@ -5572,7 +5572,8 @@ def : Flag<["-"], "nocudalib">, Alias<nogpulib>;
def gpulibc : Flag<["-"], "gpulibc">, Visibility<[ClangOption, CC1Option, FlangOption, FC1Option]>,
HelpText<"Link the LLVM C Library for GPUs">;
def nogpulibc : Flag<["-"], "nogpulibc">, Visibility<[ClangOption, CC1Option, FlangOption, FC1Option]>;
def nodefaultlibs : Flag<["-"], "nodefaultlibs">;
def nodefaultlibs : Flag<["-"], "nodefaultlibs">,
Visibility<[ClangOption, FlangOption, CLOption, DXCOption]>;
Comment on lines +5575 to +5576
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@tarunprabhu, @tblah

Shouldn't these be: Visibility<[ClangOption, FlangOption]>, it seems like clang-cl is now accepting -nodefaultlibs without diagnostic, and it does not do anything (does NOT add /NODEFAULTLIB to link.exe's command line)

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From what i was able to tell when I changed this, the lack of an explicit visibility implied these 4, but perhaps I was mistaken. I have no way to test clang-cl. Is there a test for this somewhere?

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@Maetveis Maetveis Dec 3, 2024 •
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I don't see anything invoking clang-cl if searching for -nodefaultlibs in clang tests: https://github.com/search?q=repo%3Allvm%2Fllvm-project+nodefaultlibs+path%3Aclang%2Ftest&type=code. I can check tomorrow (Europe time) if indeed the default visibility extends to clang-cl.

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With this change in Options.td:

diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index cb96b5daed9d3a2..842e6c2e6233adb 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -5644,4 +5644,3 @@ def gpulibc : Flag<["-"], "gpulibc">, Visibility<[ClangOption, CC1Option, FlangO
 def nogpulibc : Flag<["-"], "nogpulibc">, Visibility<[ClangOption, CC1Option, FlangOption, FC1Option]>;
-def nodefaultlibs : Flag<["-"], "nodefaultlibs">,
-  Visibility<[ClangOption, FlangOption, CLOption, DXCOption]>;
+def nodefaultlibs : Flag<["-"], "nodefaultlibs">;
 def nodriverkitlib : Flag<["-"], "nodriverkitlib">;

I'm getting:

> build\bin\clang-cl.exe -nodefaultlibs asd.o
clang-cl: warning: unknown argument ignored in clang-cl: '-nodefaultlibs' [-Wunknown-argument]

without it I don't get a warning.

The comment at Options.td:74 also seems to suggest the default is only the gcc compatible driver.

llvm-project/clang/include/clang/Driver/Options.td

Lines 74 to 77 in c3536b2

// We prefer the name "ClangOption" here rather than "Default" to make
// it clear that these options will be visible in the clang driver (as
// opposed to clang -cc1, the CL driver, or the flang driver).
defvar ClangOption = DefaultVis;

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I opened #118640 (comment), can you take a look?

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Just a drive-by comment.

From what i was able to tell when I changed this, the lack of an explicit visibility implied these 4, but perhaps I was mistaken.

This should be verifiable by checking Options.inc file in the build directory before and after change. Options.inc is the C++ files generated from Options.td when building clangDriver. Please use that as your guidance.

def nodriverkitlib : Flag<["-"], "nodriverkitlib">;
def nofixprebinding : Flag<["-"], "nofixprebinding">;
def nolibc : Flag<["-"], "nolibc">;
Expand All @@ -5592,7 +5593,9 @@ def nostdincxx : Flag<["-"], "nostdinc++">, Visibility<[ClangOption, CC1Option]>
Group<IncludePath_Group>,
HelpText<"Disable standard #include directories for the C++ standard library">,
MarshallingInfoNegativeFlag<HeaderSearchOpts<"UseStandardCXXIncludes">>;
def nostdlib : Flag<["-"], "nostdlib">, Group<Link_Group>;
def nostdlib : Flag<["-"], "nostdlib">,
Visibility<[ClangOption, CLOption, FlangOption, DXCOption]>,
Group<Link_Group>;
def nostdlibxx : Flag<["-"], "nostdlib++">;
def object : Flag<["-"], "object">;
def o : JoinedOrSeparate<["-"], "o">,
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3 changes: 2 additions & 1 deletion clang/lib/Driver/ToolChains/AIX.cpp
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Expand Up @@ -330,7 +330,8 @@ void aix::Linker::ConstructJob(Compilation &C, const JobAction &JA,
}
}

if (D.IsFlangMode()) {
if (D.IsFlangMode() &&
!Args.hasArg(options::OPT_nostdlib, options::OPT_nodefaultlibs)) {
addFortranRuntimeLibraryPath(ToolChain, Args, CmdArgs);
addFortranRuntimeLibs(ToolChain, Args, CmdArgs);
CmdArgs.push_back("-lm");
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3 changes: 2 additions & 1 deletion clang/lib/Driver/ToolChains/Darwin.cpp
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Expand Up @@ -713,7 +713,8 @@ void darwin::Linker::ConstructJob(Compilation &C, const JobAction &JA,

// Additional linker set-up and flags for Fortran. This is required in order
// to generate executables.
if (getToolChain().getDriver().IsFlangMode()) {
if (getToolChain().getDriver().IsFlangMode() &&
!Args.hasArg(options::OPT_nostdlib, options::OPT_nodefaultlibs)) {
addFortranRuntimeLibraryPath(getToolChain(), Args, CmdArgs);
addFortranRuntimeLibs(getToolChain(), Args, CmdArgs);
}
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3 changes: 2 additions & 1 deletion clang/lib/Driver/ToolChains/DragonFly.cpp
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Expand Up @@ -151,7 +151,8 @@ void dragonfly::Linker::ConstructJob(Compilation &C, const JobAction &JA,
// to generate executables. As Fortran runtime depends on the C runtime,
// these dependencies need to be listed before the C runtime below (i.e.
// AddRunTimeLibs).
if (D.IsFlangMode()) {
if (D.IsFlangMode() &&
!Args.hasArg(options::OPT_nostdlib, options::OPT_nodefaultlibs)) {
addFortranRuntimeLibraryPath(ToolChain, Args, CmdArgs);
addFortranRuntimeLibs(ToolChain, Args, CmdArgs);
CmdArgs.push_back("-lm");
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3 changes: 2 additions & 1 deletion clang/lib/Driver/ToolChains/FreeBSD.cpp
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Expand Up @@ -313,7 +313,8 @@ void freebsd::Linker::ConstructJob(Compilation &C, const JobAction &JA,
// to generate executables. As Fortran runtime depends on the C runtime,
// these dependencies need to be listed before the C runtime below (i.e.
// AddRunTimeLibs).
if (D.IsFlangMode()) {
if (D.IsFlangMode() &&
!Args.hasArg(options::OPT_nostdlib, options::OPT_nodefaultlibs)) {
addFortranRuntimeLibraryPath(ToolChain, Args, CmdArgs);
addFortranRuntimeLibs(ToolChain, Args, CmdArgs);
if (Profiling)
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3 changes: 2 additions & 1 deletion clang/lib/Driver/ToolChains/Gnu.cpp
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Expand Up @@ -572,7 +572,8 @@ void tools::gnutools::Linker::ConstructJob(Compilation &C, const JobAction &JA,
// to generate executables. As Fortran runtime depends on the C runtime,
// these dependencies need to be listed before the C runtime below (i.e.
// AddRunTimeLibs).
if (D.IsFlangMode()) {
if (D.IsFlangMode() &&
!Args.hasArg(options::OPT_nostdlib, options::OPT_nodefaultlibs)) {
addFortranRuntimeLibraryPath(ToolChain, Args, CmdArgs);
addFortranRuntimeLibs(ToolChain, Args, CmdArgs);
CmdArgs.push_back("-lm");
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3 changes: 2 additions & 1 deletion clang/lib/Driver/ToolChains/Haiku.cpp
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Expand Up @@ -119,7 +119,8 @@ void haiku::Linker::ConstructJob(Compilation &C, const JobAction &JA,
// to generate executables. As Fortran runtime depends on the C runtime,
// these dependencies need to be listed before the C runtime below (i.e.
// AddRunTimeLibs).
if (D.IsFlangMode()) {
if (D.IsFlangMode() &&
!Args.hasArg(options::OPT_nostdlib, options::OPT_nodefaultlibs)) {
addFortranRuntimeLibraryPath(ToolChain, Args, CmdArgs);
addFortranRuntimeLibs(ToolChain, Args, CmdArgs);
}
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3 changes: 2 additions & 1 deletion clang/lib/Driver/ToolChains/MSVC.cpp
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Expand Up @@ -138,7 +138,8 @@ void visualstudio::Linker::ConstructJob(Compilation &C, const JobAction &JA,
for (const auto &LibPath : Args.getAllArgValues(options::OPT_L))
CmdArgs.push_back(Args.MakeArgString("-libpath:" + LibPath));

if (C.getDriver().IsFlangMode()) {
if (C.getDriver().IsFlangMode() &&
!Args.hasArg(options::OPT_nostdlib, options::OPT_nodefaultlibs)) {
addFortranRuntimeLibraryPath(TC, Args, CmdArgs);
addFortranRuntimeLibs(TC, Args, CmdArgs);

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3 changes: 2 additions & 1 deletion clang/lib/Driver/ToolChains/MinGW.cpp
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Expand Up @@ -251,7 +251,8 @@ void tools::MinGW::Linker::ConstructJob(Compilation &C, const JobAction &JA,
D.getLTOMode() == LTOK_Thin);
}

if (C.getDriver().IsFlangMode()) {
if (C.getDriver().IsFlangMode() &&
!Args.hasArg(options::OPT_nostdlib, options::OPT_nodefaultlibs)) {
addFortranRuntimeLibraryPath(TC, Args, CmdArgs);
addFortranRuntimeLibs(TC, Args, CmdArgs);
}
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3 changes: 2 additions & 1 deletion clang/lib/Driver/ToolChains/NetBSD.cpp
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Expand Up @@ -326,7 +326,8 @@ void netbsd::Linker::ConstructJob(Compilation &C, const JobAction &JA,
// to generate executables. As Fortran runtime depends on the C runtime,
// these dependencies need to be listed before the C runtime below (i.e.
// AddRunTimeLibs).
if (D.IsFlangMode()) {
if (D.IsFlangMode() &&
!Args.hasArg(options::OPT_nostdlib, options::OPT_nodefaultlibs)) {
addFortranRuntimeLibraryPath(ToolChain, Args, CmdArgs);
addFortranRuntimeLibs(ToolChain, Args, CmdArgs);
CmdArgs.push_back("-lm");
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3 changes: 2 additions & 1 deletion clang/lib/Driver/ToolChains/OpenBSD.cpp
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Expand Up @@ -239,7 +239,8 @@ void openbsd::Linker::ConstructJob(Compilation &C, const JobAction &JA,
// to generate executables. As Fortran runtime depends on the C runtime,
// these dependencies need to be listed before the C runtime below (i.e.
// AddRunTimeLibs).
if (D.IsFlangMode()) {
if (D.IsFlangMode() &&
!Args.hasArg(options::OPT_nostdlib, options::OPT_nodefaultlibs)) {
addFortranRuntimeLibraryPath(ToolChain, Args, CmdArgs);
addFortranRuntimeLibs(ToolChain, Args, CmdArgs);
if (Profiling)
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3 changes: 2 additions & 1 deletion clang/lib/Driver/ToolChains/Solaris.cpp
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Expand Up @@ -223,7 +223,8 @@ void solaris::Linker::ConstructJob(Compilation &C, const JobAction &JA,
// Additional linker set-up and flags for Fortran. This is required in order
// to generate executables. As Fortran runtime depends on the C runtime,
// these dependencies need to be listed before the C runtime below.
if (D.IsFlangMode()) {
if (D.IsFlangMode() &&
!Args.hasArg(options::OPT_nostdlib, options::OPT_nodefaultlibs)) {
addFortranRuntimeLibraryPath(getToolChain(), Args, CmdArgs);
addFortranRuntimeLibs(getToolChain(), Args, CmdArgs);
CmdArgs.push_back("-lm");
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29 changes: 29 additions & 0 deletions flang/test/Driver/nostdlib.f90
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@@ -0,0 +1,29 @@
! Check that the libraries do not appear when using -nostdlib and -nodefaultlibs

! RUN: %flang -### -nostdlib --target=ppc64le-linux-gnu %s 2>&1 | FileCheck %s
! RUN: %flang -### -nostdlib --target=aarch64-apple-darwin %s 2>&1 | FileCheck %s
! RUN: %flang -### -nostdlib --target=sparc-sun-solaris2.11 %s 2>&1 | FileCheck %s
! RUN: %flang -### -nostdlib --target=x86_64-unknown-freebsd %s 2>&1 | FileCheck %s
! RUN: %flang -### -nostdlib --target=x86_64-unknown-netbsd %s 2>&1 | FileCheck %s
! RUN: %flang -### -nostdlib --target=x86_64-unknown-openbsd %s 2>&1 | FileCheck %s
! RUN: %flang -### -nostdlib --target=x86_64-unknown-dragonfly %s 2>&1 | FileCheck %s
! RUN: %flang -### -nostdlib --target=x86_64-unknown-haiku %s 2>&1 | FileCheck %s
! RUN: %flang -### -nostdlib --target=x86_64-windows-gnu %s 2>&1 | FileCheck %s

! RUN: %flang -### -nodefaultlibs --target=ppc64le-linux-gnu %s 2>&1 | FileCheck %s
! RUN: %flang -### -nodefaultlibs --target=aarch64-apple-darwin %s 2>&1 | FileCheck %s
! RUN: %flang -### -nodefaultlibs --target=sparc-sun-solaris2.11 %s 2>&1 | FileCheck %s
! RUN: %flang -### -nodefaultlibs --target=x86_64-unknown-freebsd %s 2>&1 | FileCheck %s
! RUN: %flang -### -nodefaultlibs --target=x86_64-unknown-netbsd %s 2>&1 | FileCheck %s
! RUN: %flang -### -nodefaultlibs --target=x86_64-unknown-openbsd %s 2>&1 | FileCheck %s
! RUN: %flang -### -nodefaultlibs --target=x86_64-unknown-dragonfly %s 2>&1 | FileCheck %s
! RUN: %flang -### -nodefaultlibs --target=x86_64-unknown-haiku %s 2>&1 | FileCheck %s
! RUN: %flang -### -nodefaultlibs --target=x86_64-windows-gnu %s 2>&1 | FileCheck %s

! -lgcc will not be linked on all platforms, so checking for that is redundant
! in certain cases. But it is not clear that it is worth checking for each
! platform individually.

! CHECK-NOT: "-lFortranRuntime"
! CHECK-NOT: "-lFortranDecimal"
! CHECK-NOT: "-lgcc"
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