Allow io_memory_resize to truncate to 0 bytes ##io#25706
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Allow io_memory_resize to truncate to 0 bytes ##io#25706
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The TODO asked why truncation to 0 bytes was not allowed. There was no fundamental reason - we just need to free the buffer and reset size/offset instead of calling realloc(ptr, 0) which has implementation-defined behavior. Also add a NULL guard for the RIOMalloc pointer and protect the read path from calling memcpy with a NULL source when the buffer is empty. https://claude.ai/code/session_01H9JNeHBKZngDR8pf47GeH4
Follow-up to the io_memory_resize fix: audit and fix all IO plugins for safe behavior when buffer size is zero. - io_gzip: allow resize to 0 (free buf, reset size/offset) for consistency with io_memory_resize, and guard __read memcpy when count adjusts to 0 to avoid memcpy with NULL source - io_null: fix unsigned underflow in __lseek where size-1 wraps to UT64_MAX when size is 0 (the __resize handler already supported count=0 but __lseek did not) - io_xattr: guard __close to skip write_xattr when buf is NULL after a resize to 0, avoiding passing NULL to setxattr https://claude.ai/code/session_01H9JNeHBKZngDR8pf47GeH4
Fix io_malloc __resize to guard against calling r_hex_bin2strdup with NULL buf/zero size after resize to 0 on hex:// URIs. The assertion in r_hex_bin2strdup would crash the process. Now the URI is set to "hex://" for empty buffers. Add test/db/cmd/cmd_or with 8 tests covering: - resize malloc:// to zero (reads return 0xff) - resize to zero and grow back (buffer is zeroed) - write after resize-to-zero and grow back - shrink preserves partial data - shrink + grow preserves partial data, new area zeroed - map removal after resize to zero - seek behavior after resize to zero - hex:// resize to zero and back https://claude.ai/code/session_01H9JNeHBKZngDR8pf47GeH4
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The TODO asked why truncation to 0 bytes was not allowed. There was no
fundamental reason - we just need to free the buffer and reset size/offset
instead of calling realloc(ptr, 0) which has implementation-defined behavior.
Also add a NULL guard for the RIOMalloc pointer and protect the read path
from calling memcpy with a NULL source when the buffer is empty.
https://claude.ai/code/session_01H9JNeHBKZngDR8pf47GeH4