Portable C Compiler

The Portable C Compiler (also known as pcc or sometimes pccm - portable C compiler machine) is an early compiler for the C programming language written by Stephen C. Johnson of Bell Labs in the mid-1970s,^[1] based in part on ideas proposed by Alan Snyder in 1973,^[2][3] and "distributed as the C compiler by Bell Labs... with the blessing of Dennis Ritchie."^[4]

Being one of the first compilers that could easily be adapted to output code for different computer architectures, the compiler had a long life span. It debuted in Seventh Edition Unix and shipped with BSD Unix until the release of 4.4BSD in 1994, when it was replaced by the GNU C Compiler. It was very influential in its day, so much so that at the beginning of the 1980s, the majority of C compilers were based on it.^[5] Anders Magnusson and Peter A Jonsson restarted development of pcc in 2007, rewriting it extensively to support the C99 standard.^[6]

Features

Key features of pcc are its portability and improved diagnostic capabilities. The compiler was designed so that only a few of its source files are machine-dependent. It is relatively robust to syntax errors and performs more thorough validity checks than its contemporaries.^{[according to whom?]}

The first C compiler, written by Dennis Ritchie, used a recursive descent parser, incorporated specific knowledge about the PDP-11, and relied on an optional machine-specific optimizer to improve the assembly language code it generated. In contrast, Johnson's pccm was based on a yacc-generated parser and used a more general target machine model. Both compilers produced target-specific assembly language code which they then assembled to produce linkable object modules.

Later versions of PCC, known within Bell Labs as "QCC" and "RCC," supported other target architecture models.^{[citation needed]}

The language that PCC implements is an extended version of K&R C that Bjarne Stroustrup has called "Classic C", incorporating the void return type (for functions that don't return any value), enumerations and structure assignment.^[4]

Current version

A new version of pcc, based on the original by Steve Johnson, is now maintained by Anders Magnusson.^[6] The compiler is provided under the BSD licence and its development is funded by a non-profit organization called BSD Fund. According to Magnusson:

The big benefit of it (apart from that it's BSD licensed, for license geeks) is that it is fast, 5-10 times faster than gcc, while still producing reasonable code. <...> [I]t is also quite simple to port...

– Anders Magnusson^[7]

This new version was added to the NetBSD pkgsrc and OpenBSD source trees in September 2007,^[8] and later into the main NetBSD source tree.^[9] There had been some speculation that it might eventually be used to supplant the GNU C Compiler on BSD-based operating systems,^[10] though FreeBSD^[11][12] and NetBSD^[13] are both looking to Clang as a potential replacement, and Theo de Raadt of OpenBSD asserts that pcc is not ready yet to be a gcc replacement, and the disposal of gcc is not top priority.^[14] On December 29, 2009, pcc became capable of building a functional x86 OpenBSD kernel image.^[15]

pcc version 1.0 was released on 1 April 2011.^[16] As of this release, the compiler supports x86 and x64 processor architectures and runs on NetBSD, OpenBSD, FreeBSD, various Linux distributions, and Microsoft Windows.^[17] Further development, including support for more architectures, and FORTRAN 77 and C++ front ends, is continuing as of 2022.

PCC was removed from the OpenBSD source tree in 2012.^[18] Development on it had stalled and no maintainer had stepped up to develop it into something that could make a practical alternative to GNU Compiler Collection.^[19][20]

The latest version of pcc, namely 1.1.0, was released on 10 December 2014.^[21]

See also

• Amsterdam Compiler Kit
• Clang
• Open Watcom

References

External links

• Archive at TUHS

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