Fix incorrect parameter index in WASI fd_read#2700
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In fd_read, params[2] was used for both iovcnt and out_ptr due to a copy-paste error. The out_ptr should use params[3], which is the fourth argument to fd_read (the pointer where the number of bytes read is written). This matches the correct usage in the fd_write implementation. WASI fd_read signature: fd_read(fd, iovs, iovcnt, nread) -> errno params[0] = fd params[1] = iovs (iovptr) params[2] = iovcnt params[3] = nread (out_ptr) <-- was incorrectly params[2]
sbc100
approved these changes
Feb 25, 2026
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Summary
Fix a copy-paste bug in the WASI
fd_readimplementation whereparams[2]was used for bothiovcntandout_ptr.Details
In
src/interp/interp-wasi.cc, thefd_readfunction extracts its four parameters from theparamsarray:However,
out_ptrwas incorrectly reading fromparams[2]instead ofparams[3], causing it to receive the same value asiovcnt. This meant the number of bytes read would be written to the wrong memory address.The correct behavior can be seen in the adjacent
fd_writeimplementation, which properly usesparams[3]for its output pointer.Test plan
cmake --build build --target wabt-unittests)fd_writeimplementation which correctly usesparams[3]