[llvm-bugs] [Bug 33533] New: clang errors out if .h file is specified as an input along with .c/.cpp

via llvm-bugs llvm-bugs at lists.llvm.org
Tue Jun 20 14:39:59 PDT 2017


            Bug ID: 33533
           Summary: clang errors out if .h file is specified as an input
                    along with .c/.cpp
           Product: clang
           Version: unspecified
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Driver
          Assignee: unassignedclangbugs at nondot.org
          Reporter: manojgupta at google.com
                CC: george.burgess.iv at gmail.com, llozano at chromium.org,
                    llvm-bugs at lists.llvm.org

$ cat test.c
int foo()
    return 0;

$ cat test.h
#include <stdlib.h>

$ clang -fpic -std=gnu99 -Wall -Werror -pedantic -Wall -g -o libtemp.so -shared
-Wl,-soname,libtemp.so test.c test.h

clang-5.0: error: cannot specify -o when generating multiple output files

This works with GCC however.

$ gcc -fpic -std=gnu99 -Wall -Werror -pedantic -Wall -g -o libtemp.so -shared
-Wl,-soname,libtemp.so test.c test.h   => Produces libtemp.so

Interestingly, clang does understand that this is a header file and tries to
compiler it to a pch file.

 "/usr/bin/clang-5.0" "-cc1" "-triple" "x86_64-pc-linux-gnu" "-emit-pch"
"-disable-free" "-disable-llvm-verifier" "-discard-value-names"
"-main-file-name" "d.h" "-mrelocation-model" "pic" "-pic-level" "1"
"-mthread-model" "posix" "-mdisable-fp-elim" "-fmath-errno" "-masm-verbose"
"-mconstructor-aliases" "-munwind-tables" "-fuse-init-array" "-target-cpu"
"x86-64" "-dwarf-column-info" "-debug-info-kind=limited" "-dwarf-version=4"
"-debugger-tuning=gdb" "-resource-dir" "/usr/lib64/clang/5.0.0"
"-internal-isystem" "/usr/local/include" "-internal-isystem"
"/usr/lib64/clang/5.0.0/include" "-internal-externc-isystem" "/include"
"-internal-externc-isystem" "/usr/include" "-Wall" "-Werror" "-Wall"
"-pedantic" "-std=gnu99" "-fdebug-compilation-dir" "/tmp" "-ferror-limit" "19"
"-fmessage-length" "140" "-fobjc-runtime=gcc" "-fdiagnostics-show-option"
"-fcolor-diagnostics" "-o" "libtemp.so" "-x" "c-header" "d.h"

So this is most likely an unhandled case in the lib/Driver/Driver.cpp

void Driver::BuildJobs(Compilation &C) const {

  // It is an error to provide a -o option if we are making multiple output
  // files.
  if (FinalOutput) {
    unsigned NumOutputs = 0;
    for (const Action *A : C.getActions())
      if (A->getType() != types::TY_Nothing) // =>  Should handle header
compilations here .

    if (NumOutputs > 1) {
      FinalOutput = nullptr;

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