From a64600d7af8a8ddf7f6db11f997ae228d8179fc2 Mon Sep 17 00:00:00 2001 From: Rui Ueyama Date: Tue, 22 Jan 2019 21:49:56 +0000 Subject: [PATCH] FileOutputBuffer: handle mmap(2) failure If the underlying filesystem does not support mmap system call, FileOutputBuffer may fail when it attempts to mmap an output temporary file. This patch handles such situation. Unfortunately, it looks like it is very hard to test this functionality without a filesystem that doesn't support mmap using llvm-lit. I tested this locally by passing an invalid parameter to mmap so that it fails and falls back to the in-memory buffer. Maybe that's all what we can do. I believe it is reasonable to submit this without a test. Differential Revision: https://reviews.llvm.org/D56949 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@351883 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Support/FileOutputBuffer.cpp | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/lib/Support/FileOutputBuffer.cpp b/lib/Support/FileOutputBuffer.cpp index cf21cc19c01..b0b817b4bdd 100644 --- a/lib/Support/FileOutputBuffer.cpp +++ b/lib/Support/FileOutputBuffer.cpp @@ -120,7 +120,7 @@ createInMemoryBuffer(StringRef Path, size_t Size, unsigned Mode) { return llvm::make_unique(Path, MB, Mode); } -static Expected> +static Expected> createOnDiskBuffer(StringRef Path, size_t Size, unsigned Mode) { Expected FileOrErr = fs::TempFile::create(Path + ".tmp%%%%%%%", Mode); @@ -144,10 +144,14 @@ createOnDiskBuffer(StringRef Path, size_t Size, unsigned Mode) { std::error_code EC; auto MappedFile = llvm::make_unique( File.FD, fs::mapped_file_region::readwrite, Size, 0, EC); + + // mmap(2) can fail if the underlying filesystem does not support it. + // If that happens, we fall back to in-memory buffer as the last resort. if (EC) { consumeError(File.discard()); - return errorCodeToError(EC); + return createInMemoryBuffer(Path, Size, Mode); } + return llvm::make_unique(Path, std::move(File), std::move(MappedFile)); }