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The Developing System
The developing system is based on a precompiler. It works in conjunction
with GNU G++ compiler.
From the point of view of the user, it operates after the preprocessing
phase and before the actual compilation.
We introduce some new extension for filenames. Here is a complete list:
.eco
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- ECO C++ compilation unit
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.heco
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- ECO C++ header file
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.temp
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- The result of a preprocessing of an ECO C++
compilation unit (.eco)
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.ii
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- The result of a precompiling of an ECO C++ ".temp" file
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.o
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- The result of a compilation of a ".ii" file
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The following are the steps for compiling an ECO C++ compilation unit
(.eco):
- This preprocesses the compilation unit using the C++ preprocessor
g++ -E filename.eco >filename.temp
- This precompiles filename.temp using the precompiler named eco_prec
eco_prec filename.temp >filename.ii
- This compiles filename.ii and generate a .o object module
g++ filename.ii
- The generated object module must be linked with other modules deriving
from ECO C++ or C++ compilation units.
The following figure show the pipeline.
The sequence of commands is complicated but the using of MAKE simplifies
can help.
Inside the precompiler
The precompiler is written using GNU G++.
The most part of the input is copied to the output without modification.
Only the parts related to ECO C++ primitives are modified.
To generate C++ from ECO C++ precompiler must know much information
about definitions in the source code, so a large part of the code of the
precompiler perform the manipulation the symbol database.
Much care has been posed in the analysis of the C++ entities (see ANSI
working paper on C++) to obtain a well engineered database. A hierarchy
of classes models all entities.
The following figure shows the internal structure of the precompiler:
The Substituter is a module that copies the input to the output
but can be driven to modify some part during the copy.
The front-end was built using FLEX, a lexical analyzer generator, and
BISON, a parser generator. Both are widely used and they are freely available
on the Internet. The grammar file is derived from the G++ 2.7.2 grammar,
with minor changes in the grammar part and major changes in the semantic
part. The lexical analyzer had been rewritten, but it behaves essentially
as the original G++ lexical analyzer (that is, it is context dependent).
In the following figure, it is described the hierarchy out of which
the database is built:
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