C Library Models

SmallWorld provides a number of function models for standard C functions. Models are implemented as ABI-agnostic models, and then paired with ABI-specific mixins to create platform-specific classes.

The SmallWorld model corpus is a work in progress. This page lists the status of our model support

We are planning to have at least stub models for the following API standards:

• C99

• POSIX

• Win32

ABI Support

SmallWorld currently provides basic C calling convention definitions for the following ABIs:

• System V

  • aarch64

  • amd64

  • armel (arm v5t)

  • armhf (arm v7a)

  • i386

  • mips

  • mipsel

  • mips64

  • mips64el

  • powerpc

  • riscv64

The model API currently supports six arguments, the maximum of any standard C function. The underlying calling convention model supports arbitrary arguments.

The models support variadic arguments; see the printf or scanf models for examples on how to use these.

The models do not support returning structs or multiple values.

The models have no way of expressing struct arguments passed by value.

The models currently don’t support va_list arguments. These are opaque structs defined as compiler intrinsics, making them annoying to model.

The System V i386 calling convention uses the x87 registers to return floating-point values. None of our emulators support this.

Function Support by Header

The following tables present the current status of the function models. They are grouped by API standard, and then by header file.

The options for the “support” field mean the following:

• Full: Model is complete.

• Imprecise: Model missing critical behavior. Will raise an exception unless otherwise configured.

• N/I: Not implemented, but planned.

• None: Not modeled. Will raise an exception.

C99: string.h

	Support	Notes
memchr	Full
memcmp	Full
memcpy	Full
memmove	Full
memset	Full
strchr	Full
strcmp	Full
strcoll	Imprecise	Relies on locale; prototype model.
strcpy	Full
strcspn	Full
strerror	None	Needs platform-specific lookup table.
strlen	Full
strncmp	Full
strncpy	Full
strpbrk	Full
strrchr	Full
strspn	Full
strstr	Full
strtok	Full
strxfrm	Imprecise	Relies on locale; prototype model.

C99: stdlib.h

	Support	Notes
Abs	Full
LAbs	Full
LLAbs	Full
Abort	Full
Atexit	Imprecise	Does not actually register an on-exit call.
Atof	Full	i386 ABI uses x87 registers; not supported.
Atoi	Full
Atol	Full
Atoll	Full
Calloc	Full
Div	None	Requires returning a struct by value.
LDiv	None	Requires returning a struct by value.
LLDiv	None	Requires returning a struct by value.
Exit	Full
Free	Full
Getenv	Imprecise	envp not modeled
Malloc	Full
Mblen	None	Requires locale
Mbstowcs	None	Requires locale
Mbtowc	None	Requires locale
QSort	None	Requires calling a function pointer
Rand	Full
Realloc	Full
Srand	Full
System	Imprecise	Does not actually invoke subprocess
Wcstombs	None	Requires locale
Wctomb	None	Requires locale

C99: stdio.h

	Support	Notes
Clearerror	Full
Fclose	Full
Feof	Full	No error conditions in current models
Ferror	Full
Fflush	Full
Fgetc	Full
Fgetpos	Full
Fgets	Full
Fopen	Full
Fprintf	Full
Fputc	Full
Fputs	Full
Fread	Full
Freopen	Full
Fscanf	Full
Fseek	Full
Fsetpos	Full
Ftell	Full
Fwrite	Full
Getc	Full
Getchar	Full
Printf	Full
Putc	Full
Putchar	Full
Puts	Full
Remove	Imprecise	File system model is optional
Rename	Imprecise	File system model is optional
Rewind	Full
Scanf	Full
Snprintf	Full
Sprintf	Full
Sscanf	Full
Tmpfile	Imprecise	File system model is optional
Tmpnam	Imprecise	File system model is optional
Ungetc	Full	LOTS of undefined behavor relative to other functions
Vfprintf	N/I	Varargs function. ABIs not modeled.
Vfscanf	N/I	Varargs function. ABIs not modeled.
Vprintf	N/I	Varargs function. ABIs mot modeled.
Vscanf	N/I	Varargs function. ABIs not modeled.
Vsnprintf	N/I	Varargs function. ABIs not modeled.
Vsprintf	N/I	Varargs function. ABIs not modeled.
Vsscanf	N/I	Varargs function. ABIs not modeled.