tmedicci opened a new pull request, #15772: URL: https://github.com/apache/nuttx/pull/15772
## Summary * libc/wcsrtombs: Fix the wcsrtombs() according to the POSIX standard According to https://pubs.opengroup.org/onlinepubs/9799919799/, the expected behavior for the `wcstombs()` function is that it should convert the wide-character codes stopping conversion either when a character sequence exceeds the limit of `n` total bytes or if a null byte is stored. In the first case, the null-terminated value should not be appended to the dst buffer. Currently, no null-terminator is appended to the dst buffer, even when it's expected to be appended, generating erroneous output. This can be checked with the application at https://github.com/apache/nuttx-apps/pull/2986. Please note that the same application can be built in the host system and the expected output checked against NuttX's current behavior. ## Impact The current implementation of `wcstombs` impacts all architectures. If the `dst` buffer is zero-filled before the operation, it would not generate trouble while checking for the null-terminated string. However, this may not be true if the buffer contains random data. This PR fixes the erroneous implementation. Please note that it should be fixed at `wcstombs`, once the `wcsnrtombs` (called by the previous function) is not expected to append the null-terminator. ## Testing This depends on the testing application at https://github.com/apache/nuttx-apps/pull/2986 ### On NuttX: Internal CI testing + `rv-virt:nsh`: Build with: ``` make -j distclean && ./tools/configure.sh rv-virt:nsh && kconfig-tweak -e LIBC_LOCALE && kconfig-tweak -e TESTING_WCSTOMBS && make olddefconfig && make ``` Run with: ``` $ qemu-system-riscv32 -semihosting -M virt,aclint=on -cpu rv32 -smp 1 -bios none -kernel nuttx -nographic ABC NuttShell (NSH) NuttX-10.4.0 nsh> wcstombs wcstombs Test application: Test Scenario: len is bigger than the size of the converted string. Expected the null-terminator at the end of the converted string. Return code: 13 dst buffer (as uint8_t array): 48 65 6c 6c 6f 2c 20 77 6f 72 6c 64 21 00 The character just after the return value is the null terminating character. Test Scenario: len is exactly the size of the converted string. Do not expected the null-terminator at the end of the converted string. Return code: 13 dst buffer (as uint8_t array): 48 65 6c 6c 6f 2c 20 77 6f 72 6c 64 21 aa The character just after the return value is the expected 0xaa value. No null-terminator. Test Scenario: len is smaller than the size of the converted string. Do not expected the null-terminator at the end of the converted string. Return code: 12 dst buffer (as uint8_t array): 48 65 6c 6c 6f 2c 20 77 6f 72 6c 64 aa aa The character just after the return value is the expected 0xaa value. No null-terminator. nsh> ``` ### On host system The application at https://github.com/apache/nuttx-apps/pull/2986 can be built with: ``` gcc -o wcstombs_example ../apps/testing/libc/wcstombs/wcstombs_main.c ``` Its output should be the same on target and host. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: commits-unsubscr...@nuttx.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
