69 lines
1.7 KiB
Groff
69 lines
1.7 KiB
Groff
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.TH EM_B 6
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.ad
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.SH NAME
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em_b \- ACK B compiler
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.SH SYNOPSIS
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.B ~em/lib/ack/em_b
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.RI [ options ]
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.SH DESCRIPTION
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.I em_b
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is a port of the ABC B compiler to the ACK. Interested parties will be
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interested in the upstream distribution here:
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.nf
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.sp
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https://github.com/aap/abc
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.fi
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However, the version here has been heavily modified --- bug reports should be
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filed with the ACK, not with the upstream compiler.
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.PP
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Since B was designed for machines with word addressing, some hacking is
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required to make it work on modern, byte addressed machines. The generated
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code expects B variables to contain word addresses, and then generates
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code to transform these into native addresses before use (which,
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unfortunately, impacts performance). However, the ACK's linker doesn't know
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how to emit word addresses into the program's data sections, and so a
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separate fixup stage has to happen at runtime, just before \fBmain()\fP,
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to convert the byte addresses into word addresses.
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.PP
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The end result is that using multiple source files with B is somewhat
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unwieldy, requiring each module to be explicitly named and then an extra
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stage to generate the fixup code. See the \fBack\fP(1) and \fBabmodules\fP(1)
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for details.
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.SH OPTIONS
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.I em_b
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accepts the following flags:
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.IP \-w\ \fIsize\fP
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Sets the word size, used for scaling addresses. Usually either 2 or 4.
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.IP \-B\ \fIname\fP
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Sets the name of the module currently being compiled (used to generate the
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fixup table symbol name). Defaults to \fImain\fP if not specified.
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.IP \-i\ \fIfilename\fP
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The source B file.
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.IP \-o\ \fIfilename\fP
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The output compact EM bytecode file.
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.SH SEE ALSO
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\fIack\fR(1), \fIabmodules\fR(1)
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.SH REMARKS
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It is very unlikely the \fIem_b\fP will ever be useful for anything.
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