[libc-commits] [libc] [libc][stdlib] Implement setenv() with environment management infrastructure (PR #163018)

[Michael Jones via libc-commits]

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@@ -0,0 +1,165 @@
+//===-- Implementation of internal environment utilities ------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "environ_internal.h"
+#include "config/app.h"
+#include "src/__support/CPP/string_view.h"
+#include "src/__support/macros/config.h"
+#include "src/string/memcpy.h"
+
+// We use extern "C" declarations for malloc/free/realloc instead of including
+// src/stdlib/malloc.h, src/stdlib/free.h, and src/stdlib/realloc.h. This allows
+// the implementation to work with different allocator implementations,
+// particularly in integration tests which provide a simple bump allocator. The
+// extern "C" linkage ensures we use whatever allocator is linked with the test
+// or application.
+extern "C" void *malloc(size_t);
+extern "C" void free(void *);
+extern "C" void *realloc(void *, size_t);
+
+namespace LIBC_NAMESPACE_DECL {
+namespace internal {
+
+// Minimum initial capacity for the environment array when first allocated.
+// This avoids frequent reallocations for small environments.
+constexpr size_t MIN_ENVIRON_CAPACITY = 32;
+
+// Growth factor for environment array capacity when expanding.
+// When capacity is exceeded, new_capacity = old_capacity *
+// ENVIRON_GROWTH_FACTOR.
+constexpr size_t ENVIRON_GROWTH_FACTOR = 2;
+
+// Global state for environment management
+Mutex environ_mutex(false, false, false, false);
+char **environ_storage = nullptr;
+EnvStringOwnership *environ_ownership = nullptr;
+size_t environ_capacity = 0;
+size_t environ_size = 0;
+bool environ_is_ours = false;
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michaelrj-google wrote:

this seems like a good candidate for being a class instead of just a collection of variables and functions.

https://github.com/llvm/llvm-project/pull/163018