[PATCH] D111394: [flang] Implement GET_ENVIRONMENT_VARIABLE(LENGTH)

[Diana Picus via Phabricator via llvm-commits]

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Search for the environment variable in the envp string passed to
ProgramStart.

This is not exactly equivalent to using std::getenv, which is used
elsewhere in the runtime. Using envp is better imo because:

1. it avoids having to create a null-terminated variable name string to

pass into std::getenv;

2. we can actually have some control over what we pass into envp before

starting the program (i.e. it can contain what's already in the
environment + anything else we might see fit to add; otoh controlling
what getenv has access to is not trivial, since there's nothing in the
standard for setting environment variables, so we'd have to use platform
specific functionalities).


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D111394

Files:
  flang/runtime/command.cpp
  flang/runtime/environment.cpp
  flang/runtime/environment.h
  flang/unittests/Runtime/CommandTest.cpp

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