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9efc2f4283
* Lazy-initialize the environment variables. This is the first in a series of PRs to make it easier to use WASI libc in Wasm modules that don't have a `main` function. By initializing the environment on demand, we avoid depending on having `__wasm_call_ctors` run. This uses weak symbols strategically to ensure that if `environ` is used, it is initialized eagerly, but if only `getenv` and friends are used, the environment is initialized lazily. Eventually, I expect we'll have a convention for wasm modules without main functions which will allow the `__wasm_call_ctors` function to be called automatically, but this helps in simple cases for now. Fixes #180. * Add comments explaining the libc-environ-compat.h header usage.
27 lines
1.0 KiB
C
27 lines
1.0 KiB
C
#include <unistd.h>
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#include <stdlib.h>
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#include <sysexits.h>
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#include <wasi/api.h>
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#include <wasi/libc.h>
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#include <wasi/libc-environ.h>
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// If the program does use `environ`, it'll get this version of
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// `__wasilibc_environ`, which is initialized with a constructor function, so
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// that it's initialized whenever user code might want to access it.
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char **__wasilibc_environ;
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extern __typeof(__wasilibc_environ) _environ
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__attribute__((weak, alias("__wasilibc_environ")));
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extern __typeof(__wasilibc_environ) environ
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__attribute__((weak, alias("__wasilibc_environ")));
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// We define this function here in the same source file as
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// `__wasilibc_environ`, so that this function is called in iff environment
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// variable support is used.
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// Concerning the 50 -- levels up to 100 are reserved for the implementation,
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// so we an arbitrary number in the middle of the range to allow other
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// reserved things to go before or after.
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__attribute__((constructor(50)))
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static void __wasilibc_initialize_environ_eagerly(void) {
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__wasilibc_initialize_environ();
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}
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