[clang][AVR] Set '-fno-use-cxa-atexit' to default

[benshi001]

Summary

The avr-libc does not support '__cxa_atexit()'.

[benshi001]

This comment was removed by benshi001.

[benshi001]

This comment was removed by benshi001.

[benshi001]

AVR is baremetal environment, it does not support __cxa_atexit()

[benshi001]

This comment was removed by benshi001.

[benshi001]

fixes https://github.com/llvm/llvm-project/issues/50631

[MaskRay]

LGTM.

clang/lib/CodeGen/TargetInfo.cpp

public:
   AVRTargetCodeGenInfo(CodeGenTypes &CGT)
       : TargetCodeGenInfo(std::make_unique<AVRABIInfo>(CGT)) {}
 
   LangAS getGlobalVarAddressSpace(CodeGenModule &CGM,
                                   const VarDecl *D) const override {
     // Check if global/static variable is defined in address space
     // 1~6 (__flash, __flash1, __flash2, __flash3, __flash4, __flash5)
     // but not constant.
+    if (D) {
       LangAS AS = D->getType().getAddressSpace();
       if (isTargetAddressSpace(AS) && 1 <= toTargetAddressSpace(AS) &&
           toTargetAddressSpace(AS) <= 6 && !D->getType().isConstQualified())
         CGM.getDiags().Report(D->getLocation(),
                               diag::err_verify_nonconst_addrspace)
             << "__flash*";
+    }
     return TargetCodeGenInfo::getGlobalVarAddressSpace(CGM, D);
   }
 
   void setTargetAttributes(const Decl *D, llvm::GlobalValue *GV,
                            CodeGen::CodeGenModule &CGM) const override {
     if (GV->isDeclaration())
       return;
     const auto *FD = dyn_cast_or_null<FunctionDecl>(D);

clang/lib/Driver/ToolChains/AVR.cpp

 void AVRToolChain::addClangTargetOptions(
     const llvm::opt::ArgList &DriverArgs, llvm::opt::ArgStringList &CC1Args,
     Action::OffloadKind DeviceOffloadKind) const {
   // By default, use `.ctors` (not `.init_array`), as required by libgcc, which
   // runs constructors/destructors on AVR.
   if (!DriverArgs.hasFlag(options::OPT_fuse_init_array,
                           options::OPT_fno_use_init_array, false))
     CC1Args.push_back("-fno-use-init-array");
+  // Use `-fno-use-cxa-atexit` as default, since avr-libc does not support
+  // `__cxa_atexit()`.
+  if (!DriverArgs.hasFlag(options::OPT_fuse_cxa_atexit,
+                          options::OPT_fno_use_cxa_atexit, false))
+    CC1Args.push_back("-fno-use-cxa-atexit");
 }
 
 Tool *AVRToolChain::buildLinker() const {
   return new tools::AVR::Linker(getTriple(), *this, LinkStdlib);
 }
 
 void AVR::Linker::ConstructJob(Compilation &C, const JobAction &JA,
                                const InputInfo &Output,

clang/test/Driver/avr-toolchain.c

 
 // RUN: %clang %s -### -target avr --sysroot %S/Inputs/basic_avr_tree_2 -S 2>&1 | FileCheck --check-prefix=CHECK3 %s
 // CHECK3: clang{{.*}} "-cc1" "-triple" "avr"
 // CHECK3-SAME: "-isysroot" "[[SYSROOT:[^"]+/basic_avr_tree_2]]"
 // CHECK3-SAME: "-internal-isystem"
 // CHECK3-SAME: {{^}} "[[SYSROOT]]/usr/avr/include"
 
 // RUN: %clang %s -### -target avr 2>&1 | FileCheck -check-prefix=CC1 %s
-// CC1: clang{{.*}} "-cc1" "-triple" "avr" {{.*}} "-fno-use-init-array"
+// CC1: clang{{.*}} "-cc1" "-triple" "avr" {{.*}} "-fno-use-init-array" "-fno-use-cxa-atexit"
+
+// RUN: %clang %s -### -target avr -fuse-init-array -fuse-cxa-atexit 2>&1 | FileCheck -check-prefix=CHECK4 %s
+// CHECK4: clang{{.*}} "-cc1" "-triple" "avr"
+// CHECK4-NOT: "-fno-use-init-array"
+// CHECK4-NOT: "-fno-use-cxa-atexit"
 
 // RUN: %clang %s -### -target avr --sysroot %S/Inputs/basic_avr_tree 2>&1 -nostdinc | FileCheck --check-prefix=NOSTDINC %s
 // RUN: %clang %s -### -target avr --sysroot %S/Inputs/basic_avr_tree 2>&1 -nostdlibinc | FileCheck --check-prefix=NOSTDINC %s
 // NOSTDINC-NOT: "-internal-isystem" {{".*avr/include"}}