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_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.