feat(c-api) Handle initialized but empty results in wasm_func_call
#1783
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Our implementation of `wasm_func_call` was correct for C code as follows: ```c wasm_val_vec_t arguments = WASM_EMPTY_VEC; wasm_val_vec_t results = WASM_EMPTY_VEC; wasm_func_call(func, &arguments, &results); ``` However, for a C code such as: ```c wasm_val_t vals[1]; wasm_val_vec_t arguments = WASM_EMPTY_VEC; wasm_val_vec_t results = WASM_ARRAY_VEC(vals); wasm_func_call(func, &arguments, &results); ``` the `vals` array were kept empty/unchanged. Why? Because `wasm_func_call` was replacing the value of `results` by a new `wasm_val_vec_t`. It is correct when `results` is an empty vector, but it is incorrect when `results` is initialized with empty values. This patch tries to detect this pattern: If `results.data` is `null`, it means the vector is empty/uninitialized, and we can set a new `wasm_val_vec_t`, otherwise it means the vector is initialized with empty values, and we need to update each item individually.
Hywan
added
🎉 enhancement
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Opened question: Do we need to error when the size of |
…lized-results-memory test(c-api) Enable the memory test example.
Hywan
commented
Oct 30, 2020
…b.com:Hywan/wasmer into feat-c-api-func-call-with-initialized-results
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bors try |
tryBuild succeeded: |
jubianchi
approved these changes
Oct 30, 2020
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bors r+ |
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Build succeeded: |
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Description
Our implementation of
wasm_func_callwas correct for C code asfollows:
However, for a C code such as:
the
valsarray were kept empty/unchanged. Why?Because
wasm_func_callwas replacing the value ofresultsby a newwasm_val_vec_t. It is correct whenresultsis an empty vector, butit is incorrect when
resultsis initialized with empty values.This patch tries to detect this pattern: If
results.dataisnull,it means the vector is empty/uninitialized, and we can set a new
wasm_val_vec_t, otherwise it means the vector is initialized withempty values, and we need to update each item individually.
This pattern can be found in the
global.cexample of the Wasm C API:wasmer/lib/c-api/tests/wasm_c_api/wasm-c-api/example/global.c
Lines 40 to 47 in 591691b
Without this patch, this test fails.
Review