[clang][driver] Special care for -l flags in config files

Currently, if a -l flag is added into a config file (e.g. clang.cfg),
it is situated before any object file in the effective command
line. If the library requested by given -l flag is static, its
symbols will not be made visible to any of the object files provided
by the user. Also, the presence of any of the -l flags in a config
file confuses the driver whenever the user invokes clang without
any parameters.

This patch solves both of those problems, by moving the -lm flags
specified in a config file to the end of the input list, and by
discarding them when there are no other inputs provided by the user,
or the last phase is not the linking phase.

Author: pawosm-arm

clang/include/clang/Driver/Driver.h

@@ -297,6 +297,9 @@ class Driver {
   /// Object that stores strings read from configuration file.
   llvm::StringSaver Saver;
 
+  /// Linker inputs originated from configuration file.
+  std::unique_ptr<llvm::opt::InputArgList> CfgLinkerInputs;
+
   /// Arguments originated from configuration file.
   std::unique_ptr<llvm::opt::InputArgList> CfgOptions;
 

clang/lib/Driver/Driver.cpp

@@ -1062,6 +1062,15 @@ bool Driver::readConfigFile(StringRef FileName,
   for (Arg *A : *NewOptions)
     A->claim();
 
+  std::unique_ptr<InputArgList> NewLinkerIns = std::make_unique<InputArgList>();
+  for (Arg *A : NewOptions->filtered(options::OPT_l)) {
+    const Arg *BaseArg = &A->getBaseArg();
+    if (BaseArg == A)
+      BaseArg = nullptr;
+    appendOneArg(*NewLinkerIns, A, BaseArg);
+  }
+  NewOptions->eraseArg(options::OPT_l);
+
   if (!CfgOptions)
     CfgOptions = std::move(NewOptions);
   else {
@@ -1073,6 +1082,19 @@ bool Driver::readConfigFile(StringRef FileName,
       appendOneArg(*CfgOptions, Opt, BaseArg);
     }
   }
+
+  if (!CfgLinkerInputs)
+    CfgLinkerInputs = std::move(NewLinkerIns);
+  else {
+    // If this is a subsequent config file, append options to the previous one.
+    for (auto *Opt : *NewLinkerIns) {
+      const Arg *BaseArg = &Opt->getBaseArg();
+      if (BaseArg == Opt)
+        BaseArg = nullptr;
+      appendOneArg(*CfgLinkerInputs, Opt, BaseArg);
+    }
+  }
+
   ConfigFiles.push_back(std::string(CfgFileName));
   return false;
 }
@@ -1250,6 +1272,7 @@ Compilation *Driver::BuildCompilation(ArrayRef<const char *> ArgList) {
   if (!ContainsError)
     ContainsError = loadConfigFiles();
   bool HasConfigFile = !ContainsError && (CfgOptions.get() != nullptr);
+  bool HasConfigLinkerIn = !ContainsError && (CfgLinkerInputs.get() != nullptr);
 
   // All arguments, from both config file and command line.
   InputArgList Args = std::move(HasConfigFile ? std::move(*CfgOptions)
@@ -1552,6 +1575,15 @@ Compilation *Driver::BuildCompilation(ArrayRef<const char *> ArgList) {
   // Construct the list of inputs.
   InputList Inputs;
   BuildInputs(C->getDefaultToolChain(), *TranslatedArgs, Inputs);
+  if (HasConfigLinkerIn && Inputs.size()) {
+    Arg *FinalPhaseArg;
+    if (getFinalPhase(*TranslatedArgs, &FinalPhaseArg) == phases::Link) {
+      DerivedArgList TranslatedLinkerIns(*CfgLinkerInputs);
+      for (Arg *A : *CfgLinkerInputs)
+        TranslatedLinkerIns.append(A);
+      BuildInputs(C->getDefaultToolChain(), TranslatedLinkerIns, Inputs);
+    }
+  }
 
   // Populate the tool chains for the offloading devices, if any.
   CreateOffloadingDeviceToolChains(*C, Inputs);

clang/test/Driver/Inputs/config-l-openmp.cfg

@@ -0,0 +1 @@
+-Wall -fopenmp -lm -lhappy

clang/test/Driver/Inputs/config-l.cfg

@@ -0,0 +1 @@
+-Wall -lm -lhappy

clang/test/Driver/config-file.c

@@ -82,3 +82,22 @@
 // CHECK-TWO-CONFIGS: -isysroot
 // CHECK-TWO-CONFIGS-SAME: /opt/data
 // CHECK-TWO-CONFIGS-SAME: -Wall
+
+//--- The -l flags should be moved to the end of input list and appear only when linking.
+// RUN: %clang --config %S/Inputs/config-l.cfg -o %s.out %s -### 2>&1 | FileCheck %s -check-prefix CHECK-LINKING
+// RUN: %clang --config %S/Inputs/config-l-openmp.cfg -o %s.out %s -### 2>&1 | FileCheck %s -check-prefix CHECK-LINKING-LIBOMP-GOES-LAST
+// RUN: %clang --config %S/Inputs/config-l.cfg -S %s -### 2>&1 | FileCheck %s -check-prefix CHECK-NOLINKING
+// RUN: %clang --config %S/Inputs/config-l-openmp.cfg -S %s -### 2>&1 | FileCheck %s -check-prefix CHECK-NOLINKING
+// CHECK-LINKING: Configuration file: {{.*}}Inputs{{.}}config-l.cfg
+// CHECK-LINKING: "-Wall"
+// CHECK-LINKING: "/tmp/{{.*}}-{{.*}}.o" "-lm" "-lhappy"
+// CHECK-LINKING-LIBOMP-GOES-LAST: Configuration file: {{.*}}Inputs{{.}}config-l-openmp.cfg
+// CHECK-LINKING-LIBOMP-GOES-LAST: "-Wall"
+// CHECK-LINKING-LIBOMP-GOES-LAST-SAME: "-fopenmp"
+// CHECK-LINKING-LIBOMP-GOES-LAST: "/tmp/{{.*}}-{{.*}}.o" "-lm" "-lhappy"
+// CHECK-LINKING-LIBOMP-GOES-LAST-SAME: "-lomp"
+// CHECK-NOLINKING: Configuration file: {{.*}}Inputs{{.}}config-l{{.*}}.cfg
+// CHECK-NOLINKING: "-Wall"
+// CHECK-NOLINKING-NO: "-lm"
+// CHECK-NOLINKING-NO: "-lhappy"
+// CHECK-NOLINKING-NO: "-lomp"

flang/test/Driver/Inputs/config-l-openmp.cfg

@@ -0,0 +1 @@
+-ffast-math -fopenmp -lm -lhappy

flang/test/Driver/Inputs/config-l.cfg

@@ -0,0 +1 @@
+-ffast-math -lm -lhappy

flang/test/Driver/config-file.f90

@@ -61,3 +61,22 @@
 ! CHECK-TWO-CONFIGS-NEXT: Configuration file: {{.*}}Inputs{{.}}config2{{.}}config-4.cfg
 ! CHECK-TWO-CONFIGS: -ffp-contract=fast
 ! CHECK-TWO-CONFIGS: -O3
+
+!--- The -l flags should be moved to the end of input list and appear only when linking.
+! RUN: %flang --config %S/Inputs/config-l.cfg -o %s.out %s -### 2>&1 | FileCheck %s -check-prefix CHECK-LINKING
+! RUN: %flang --config %S/Inputs/config-l-openmp.cfg -o %s.out %s -### 2>&1 | FileCheck %s -check-prefix CHECK-LINKING-LIBOMP-GOES-LAST
+! RUN: %flang --config %S/Inputs/config-l.cfg -S %s -### 2>&1 | FileCheck %s -check-prefix CHECK-NOLINKING
+! RUN: %flang --config %S/Inputs/config-l-openmp.cfg -S %s -### 2>&1 | FileCheck %s -check-prefix CHECK-NOLINKING
+! CHECK-LINKING: Configuration file: {{.*}}Inputs{{.}}config-l.cfg
+! CHECK-LINKING: "-ffast-math"
+! CHECK-LINKING: "/tmp/{{.*}}-{{.*}}.o" "-lm" "-lhappy"
+! CHECK-LINKING-LIBOMP-GOES-LAST: Configuration file: {{.*}}Inputs{{.}}config-l-openmp.cfg
+! CHECK-LINKING-LIBOMP-GOES-LAST: "-ffast-math"
+! CHECK-LINKING-LIBOMP-GOES-LAST-SAME: "-fopenmp"
+! CHECK-LINKING-LIBOMP-GOES-LAST: "/tmp/{{.*}}-{{.*}}.o" "-lm" "-lhappy"
+! CHECK-LINKING-LIBOMP-GOES-LAST-SAME: "-lomp"
+! CHECK-NOLINKING: Configuration file: {{.*}}Inputs{{.}}config-l{{.*}}.cfg
+! CHECK-NOLINKING: "-ffast-math"
+! CHECK-NOLINKING-NO: "-lm"
+! CHECK-NOLINKING-NO: "-lhappy"
+! CHECK-NOLINKING-NO: "-lomp"