Reid Kleckner cc418a3af4 [Support] Move llvm::MemoryBuffer to sys::fs::file_t
Summary:
On Windows, Posix integer file descriptors are a compatibility layer
over native file handles provided by the C runtime. There is a hard
limit on the maximum number of file descriptors that a process can open,
and the limit is 8192. LLD typically doesn't run into this limit because
it opens input files, maps them into memory, and then immediately closes
the file descriptor. This prevents it from running out of FDs.

For various reasons, I'd like to open handles to every input file and
keep them open during linking. That requires migrating MemoryBuffer over
to taking open native file handles instead of integer FDs.

Reviewers: aganea, Bigcheese

Reviewed By: aganea

Subscribers: smeenai, silvas, mehdi_amini, hiraditya, steven_wu, dexonsmith, dang, llvm-commits, zturner

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D63453

llvm-svn: 365588
2019-07-10 00:34:13 +00:00
..

llvm/lib/Support/Unix README
===========================

This directory provides implementations of the lib/System classes that
are common to two or more variants of UNIX. For example, the directory
structure underneath this directory could look like this:

Unix           - only code that is truly generic to all UNIX platforms
  Posix        - code that is specific to Posix variants of UNIX
  SUS          - code that is specific to the Single Unix Specification
  SysV         - code that is specific to System V variants of UNIX

As a rule, only those directories actually needing to be created should be
created. Also, further subdirectories could be created to reflect versions of
the various standards. For example, under SUS there could be v1, v2, and v3
subdirectories to reflect the three major versions of SUS.