String Functions

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

✅

bcmp

✅

bcopy

✅

memcpy

✅

memset

✅

memcmp

✅

memmove

✅

Other Raw Memory Functions

Function Name

Available

memchr

✅

memrchr

✅

memccpy

✅

mempcpy

✅

String Memory Functions

Function Name

Available

stpcpy

✅

stpncpy

✅

strcpy

✅

strncpy

✅

strcat

✅

strncat

✅

strdup

✅

strndup

✅

String Examination Functions

Function Name

Available

strlen

✅

strnlen

✅

strcmp

✅

strncmp

✅

strchr

✅

strrchr

✅

strspn

✅

strcspn

✅

strpbrk

✅

strstr

✅

strtok

✅

strtok_r

✅

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

✅

atoi

✅

atol

✅

atoll

✅

strtol

✅

strtoll

✅

strtoul

✅

strtoull

✅

strtof

✅

strtod

✅

strtold

✅

strtoimax

✅

strtoumax

✅

String Error Functions

Function Name

Available

strerror

✅

strerror_r

✅

Localized String Functions

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

Function Name

Available

strcoll

Partially

strxfrm

Partially

<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.