View source for Cfront

{{Short description|Original compiler for C++}}
'''Cfront''' was the original [[compiler]] for [[C++]] (then known as "[[C (programming language)|C]] with Classes") from around 1983, which converted C++ to C; developed by [[Bjarne Stroustrup]] at AT&T Bell Labs. The [[preprocessor]] did not understand all of the [[programming language|language]] and much of the [[source code|code]] was written via [[Source-to-source compiler|translations]]. Cfront had a complete [[parser]], built [[symbol table]]s, and built a [[tree data structure|tree]] for each [[class (computer science)|class]], [[function (programming)|function]], etc. Cfront was based on CPre, a C compiler started in 1979.

As Cfront was written in C++, it was a challenge to [[bootstrapping (compilers)|bootstrap]] on a machine without a C++ compiler/translator.  Along with the Cfront C++ sources, a special "half-preprocessed" version of the C code resulting from compiling Cfront with itself was also provided. This C code was to be compiled with the native C compiler, and the resulting executable could then be used to compile the Cfront C++ sources.

Most of the porting effort in getting Cfront running on a new machine was related to standard I/O. Cfront's C++ streams were closely tied in with the C library's buffered I/O streams, but there was little  interaction with the rest of the C environment. The compiler could be ported to most [[System V]] derivatives without many changes, but [[BSD]]-based systems usually had many more variations in their C libraries and associated stdio structures.

Cfront defined the language until circa 1990, and many of the more obscure corner cases in C++ were related to its C++-to-C translation approach. A few remnants of Cfront's translation method are still found in today's C++ compilers; [[name mangling]] was originated by Cfront, as the relatively primitive [[Linker (computing)|linkers]] at the time did not support type information in symbols, and some template instantiation models are derived from Cfront's early efforts. C++ (and Cfront) was directly responsible for many improvements in [[Unix]] linkers and  [[object file]] [[file format|format]]s, as it was the first widely used language which required link-time type checking, [[weak symbol]]s, and other similar features.

Cfront 4.0 was abandoned in 1993 after a failed attempt to add [[exception handling|exception]] support.<ref>[[Scott Meyers]], [http://www.artima.com/cppsource/top_cpp_software.html The Most Important C++ Software...Ever], 2006</ref> The C++ language had grown beyond its capabilities; however a compiler with similar approach became available later, namely [[Comeau C/C++]].

Analogous to the way cfront can process C++ source code into something that can be compiled by previously-available C compilers, '''cppfront''' processes source code written in new and experimental C++ 'syntax 2' into something that can be compiled by previously-available 'syntax 1' C++ compilers.<ref>
[https://www.google.com/books/edition/Professional_C++/lSabEAAAQBAJ "Professional C++ Philosophy and Principles"].
2022.
p. 373.
</ref><ref>
Paul Krill.
[https://www.infoworld.com/article/3674213/cppfront-project-aims-to-modernize-c.html "Cppfront project aims to modernize C++"].
InfoWorld.
</ref>  '''cppfront''' is different in scope in that it doesn't perform many validity checks on the code, instead relying on the C++ compiler for any checks that would require non-local understanding of the code such as establishing correct use of [[Symbol table|symbols]].  Cfront on the other hand was a complete compiler that just happened to target the C language instead of an [[Assembly language|assembler]].

== References ==
{{reflist}}
;Notes
* {{cite web | url=http://stroustrup.com/hopl-almost-final.pdf | title=Evolving a language in and for the real world: C++ 1991-2006 | author=Bjarne Stroustrup | archive-url=https://web.archive.org/web/20071120015600/http://www.research.att.com/~bs/hopl-almost-final.pdf | archive-date=2007-11-20 }}
* {{cite web | url=http://stroustrup.com/bs_faq.html#bootstrapping | title=Bjarne Stroustrup's FAQ | author=Bjarne Stroustrup }}
* {{cite web | url=http://stroustrup.com/dne.html | title=The Design and Evolution of C++ | author=Bjarne Stroustrup }}

== External links ==
* [http://www.softwarepreservation.org/projects/c_plus_plus/index.html#cfront Cfront Releases] at [http://www.softwarepreservation.org/projects/c_plus_plus C++ Historical Sources Archive]
* [https://github.com/seyko2/cfront-3 cfront v3], the cfront re-port for the 4th edition of [[Plan 9 from Bell Labs]]
* [https://github.com/farisawan-2000/cfront-3 Cfront 3.0.3], "AT&T/Bell Labs C++ to C translator from 1994, modified to build on modern hardware"

[[Category:C++ compilers]]
[[Category:Unix programming tools]]

[[fr:Cfront]]