String Functions in LLVM-libc

Summary

This site tracks the status of the implementation of string functions in LLVM Libc. This includes a few extra functions that are not in string.h, such as functions converting strings to numbers.

Source location

  • The main source for string functions is located at: libc/src/string.
  • The source for string conversion functions is located at: libc/src/stdlib and libc/src/__support.
  • The tests are located at: libc/test/src/string, libc/test/src/stdlib, and libc/test/src/__support respectively.

Implementation Status

Primary memory functions

Function Name Available
bzero YES
bcmp YES
memcpy YES
memset YES
memcmp YES
memmove YES

Other Raw Memory Functions

Function Name Available
memchr YES
memrchr YES
memccpy YES
mempcpy YES

String Memory Functions

Function Name Available
stpcpy YES
stpncpy YES
strcpy YES
strncpy YES
strcat YES
strncat YES
strdup YES
strndup YES

String Examination Functions

Function Name Available
strlen YES
strnlen YES
strcmp YES
strncmp YES
strchr YES
strrchr YES
strspn YES
strcspn YES
strpbrk YES
strstr YES
strtok YES
strtok_r YES

String Conversion Functions

These functions are not in strings.h, but are still primarily string functions, and are therefore tracked along with the rest of the string functions.

The String to float functions were implemented using the Eisel-Lemire algorithm (read more about the algorithm here: The Eisel-Lemire ParseNumberF64 Algorithm). This improved the performance of string to float and double, and allowed it to complete this comprehensive test 15% faster than glibc: Parse Number FXX Test Data. The test was done with LLVM-libc built on 2022-04-14 and Debian GLibc version 2.33-6. The targets libc_str_to_float_comparison_test and libc_system_str_to_float_comparison_test were built and run on the test data 10 times each, skipping the first run since it was an outlier.

Function Name Available
atof YES
atoi YES
atol YES
atoll YES
strtol YES
strtoll YES
strtoul YES
strtoull YES
strtof YES
strtod YES
strtold YES
strtoimax YES
strtoumax YES

String Error Functions

Function Name Available
strerror  
strerror_s  
strerrorlen_s  

Localized String Functions

These functions require locale.h, and will be added when locale support is implemented in LLVM-libc.

Function Name Available
strcoll  
strxfrm  

<name>_s String Functions

Many String functions have an equivalent _s version, which is intended to be more secure and safe than the previous standard. These functions add runtime error detection and overflow protection. While they can be seen as an improvement, adoption remains relatively low among users. In addition, they are being considered for removal, see Field Experience With Annex K — Bounds Checking Interfaces. For these reasons, there is no ongoing work to implement them.