[llvm-bugs] [Bug 27491] New: compiler response file isn't used when command line is close to response file limit

via llvm-bugs llvm-bugs at lists.llvm.org
Fri Apr 22 16:27:32 PDT 2016


            Bug ID: 27491
           Summary: compiler response file isn't used when command line is
                    close to response file limit
           Product: clang
           Version: 3.7
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++
          Assignee: unassignedclangbugs at nondot.org
          Reporter: dvaliant at ea.com
                CC: dgregor at apple.com, llvm-bugs at lists.llvm.org
    Classification: Unclassified


On windows 7 it appears clang calls itself as a subprocess when used to
compile. For short command lines subprocess is called with all arguments on
command line for large command lines a response file is used. However it
appears if command line used for subprocess is only just over the limit clang
will not use a response file when it should and fail with: 

clang++.exe : error : unable to execute command: Couldn't execute program
'C:\some\system\path\LLVM\bin\clang++.exe'The filename or extension is too

Problem appears more frequently the longer the absolute path to clang++.exe


- Call clang++.exe to compile any simple cpp file using a response file, use -v
argument to see if clang uses response file when calling clang subprocess
- artificially inflate response file by adding defines (e.g -D BLOAT) until you
see above error message (will happen close 32768 characters)
- if you see clang using response file try trimming response file by a
character at a time, the range is very small (bad range seems to be length of
executable path)

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