GNU M4 macro processor v1.4.18手册

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"GNU M4 英文版.pdf" 是一份关于 GNU M4 的手册，适用于版本 1.4.18。这份手册由 René Seindal, François Pinard, Gary V. Vaughan 和 Eric Blake 编写，旨在介绍这个强大的宏处理器。 GNU M4 是一个实现了 m4 宏语言的软件包，它允许用户定义和使用宏来扩展文本处理能力。自 1989 年以来，GNU M4 经历了多次更新和改进，版本 1.4.18 是截至 2016 年 12 月 31 日的最新版本。该文档的目的是为用户提供关于如何使用 GNU M4 的详细指南。文档内容涵盖了从基本概念到高级特性的各种主题，包括： 1. **简介与预备知识**：这部分介绍了 m4 的基本概念，如为什么需要宏处理器以及它的历史背景。还提到了可能遇到的问题和已知的 bug，以及如何有效地使用这份手册。 2. **调用 m4**：这一章节详细阐述了如何启动和配置 m4。它包括了不同操作模式的命令行选项，如改变预处理器的特性、控制限制、使用冻结状态等。这些选项允许用户根据自己的需求定制 m4 的行为。 - **命令行选项**：分为几个子类别，比如用于操作模式的选项（7 页开始），预处理器功能的选项（8 页），限制控制的选项（10 页），以及与冻结状态相关的选项（11 页）。这些选项提供了对 m4 行为的精细控制。 3. **宏和输入处理**：手册后续部分会详细介绍 m4 如何处理输入文本，包括宏的定义、扩展、递归，以及如何处理包含文件、条件语句和循环结构。 4. **内置函数和特殊宏**：m4 提供了一系列内置函数和特殊宏，例如 `changeword`、`divert`、`ifelse` 等，这些在处理文本时非常有用。手册会解释它们的作用和用法。 5. **错误处理和调试**：当 m4 遇到问题时，它会生成错误消息。这部分将解释如何解读这些消息以进行问题定位和修复。 6. **性能和优化**：对于处理大量文本或复杂宏的用户，手册会提供一些性能优化的建议。 7. **其他资源和社区支持**：除了手册之外，还有其他资源可供学习和寻求帮助，如邮件列表、在线文档和社区论坛。 8. **GNU Free Documentation License**：手册遵循 GNU Free Documentation License 1.3 或更高版本发布，这意味着任何人都可以自由地复制、分发和修改这份文档。通过深入学习这份手册，用户可以熟练掌握 GNU M4，从而在文本处理、脚本编写和软件构建等场景中充分利用其强大的宏处理能力。

10 GNU M4 1.4.18 macro processor

goodbye

⇒

#line 12

⇒

goodbye

-U name

--undefine=name

This deletes any predeﬁned meaning name might have. Obviously, only prede-

ﬁned macros can be deleted in this way. This option may be given more than

once; undeﬁning a name that does not have a deﬁnition is silently ignored.

Order is signiﬁcant with respect to ﬁle names.

2.3 Command line options for limits control

There are some limits within m4 that can be tuned. For compatibility, m4 also accepts

some options that control limits in other implementations, but which are automatically

unbounded (limited only by your hardware and operating system constraints) in GNU m4.

-g

--gnu Enable all the extensions in this implementation. In this release of M4, this op-

tion is always on by default; it is currently only useful when overriding a prior

use of --traditional. However, having GNU behavior as default makes it

impossible to write a strictly POSIX-compliant client that avoids all incompat-

ible GNU M4 extensions, since such a client would have to use the non-POSIX

command-line option to force full POSIX behavior. Thus, a future version of

M4 will be changed to implicitly use the option --traditional if the environ-

ment variable POSIXLY_CORRECT is set. Projects that intentionally use GNU

extensions should consider using --gnu to state their intentions, so that the

project will not mysteriously break if the user upgrades to a newer M4 and has

POSIXLY_CORRECT set in their environment.

-G

--traditional

Suppress all the extensions made in this implementation, compared to the Sys-

tem V version. See Chapter 16 [Compatibility], page 109, for a list of these.

-H num

--hashsize=num

Make the internal hash table for symbol lookup be num entries big. For better

performance, the number should be prime, but this is not checked. The default

is 509 entries. It should not be necessary to increase this value, unless you

deﬁne an excessive number of macros.

-L num

--nesting-limit=num

Artiﬁcially limit the nesting of macro calls to num levels, stopping program

execution if this limit is ever exceeded. When not speciﬁed, nesting defaults

to unlimited on platforms that can detect stack overﬂow, and to 1024 levels

otherwise. A value of zero means unlimited; but then heavily nested code could

potentially cause a stack overﬂow.

Chapter 2: Invoking m4 11

The precise eﬀect of this option is more correctly associated with textual nesting

than dynamic recursion. It has been useful when some complex m4 input was

generated by mechanical means, and also in diagnosing recursive algorithms

that do not scale well. Most users never need to change this option from its

default.

This option does not have the ability to break endless rescanning loops, since

these do not necessarily consume much memory or stack space. Through clever

usage of rescanning loops, one can request complex, time-consuming computa-

tions from m4 with useful results. Putting limitations in this area would break

m4 power. There are many pathological cases: ‘define(‘a’, ‘a’)a’ is only the

simplest example (but see Chapter 16 [Compatibility], page 109). Expecting

GNU m4 to detect these would be a little like expecting a compiler system to

detect and diagnose endless loops: it is a quite hard problem in general, if not

undecidable!

-B num

-S num

-T num These options are present for compatibility with System V m4, but do nothing

in this implementation. They may disappear in future releases, and issue a

warning to that eﬀect.

-N num

--diversions=num

These options are present only for compatibility with previous versions of GNU

m4, and were controlling the number of possible diversions which could be used

at the same time. They do nothing, because there is no ﬁxed limit anymore.

They may disappear in future releases, and issue a warning to that eﬀect.

2.4 Command line options for frozen state

GNU m4 comes with a feature of freezing internal state (see Chapter 15 [Frozen ﬁles],

page 105). This can be used to speed up m4 execution when reusing a common initialization

script.

-F file

--freeze-state=file

Once execution is ﬁnished, write out the frozen state on the speciﬁed ﬁle. It is

conventional, but not required, for ﬁle to end in ‘.m4f’.

-R file

--reload-state=file

Before execution starts, recover the internal state from the speciﬁed frozen ﬁle.

The options -D, -U, and -t take eﬀect after state is reloaded, but before the

input ﬁles are read.

2.5 Command line options for debugging

Finally, there are several options for aiding in debugging m4 scripts.

12 GNU M4 1.4.18 macro processor

-d[flags]

--debug[=flags]

Set the debug-level according to the ﬂags ﬂags. The debug-level controls the

format and amount of information presented by the debugging functions. See

Section 7.3 [Debug Levels], page 58, for more details on the format and meaning

of ﬂags. If omitted, ﬂags defaults to ‘aeq’.

--debugfile[=file]

-o file

--error-output=file

Redirect dumpdef output, debug messages, and trace output to the named ﬁle.

Warnings, error messages, and errprint output are still printed to standard

error. If these options are not used, or if ﬁle is unspeciﬁed (only possible for

--debugfile), debug output goes to standard error; if ﬁle is the empty string,

debug output is discarded. See Section 7.4 [Debug Output], page 60, for more

details. The option --debugfile may be given more than once, and order is

signiﬁcant with respect to ﬁle names. The spellings -o and --error-output

are misleading and inconsistent with other GNU tools; for now they are silently

accepted as synonyms of --debugfile and only recognized once, but in a future

version of M4, using them will cause a warning to be issued.

-l num

--arglength=num

Restrict the size of the output generated by macro tracing to num characters

per trace line. If unspeciﬁed or zero, output is unlimited. See Section 7.3

[Debug Levels], page 58, for more details.

-t name

--trace=name

This enables tracing for the macro name, at any point where it is deﬁned. name

need not be deﬁned when this option is given. This option may be given more

than once, and order is signiﬁcant with respect to ﬁle names. See Section 7.2

[Trace], page 55, for more details.

2.6 Specifying input ﬁles on the command line

The remaining arguments on the command line are taken to be input ﬁle names. If no

names are present, standard input is read. A ﬁle name of - is taken to mean standard

input. It is conventional, but not required, for input ﬁles to end in ‘.m4’.

The input ﬁles are read in the sequence given. Standard input can be read more than

once, so the ﬁle name - may appear multiple times on the command line; this makes a

diﬀerence when input is from a terminal or other special ﬁle type. It is an error if an input

ﬁle ends in the middle of argument collection, a comment, or a quoted string.

The options --define (-D), --undefine (-U), --synclines (-s), and --trace (-t) only

take eﬀect after processing input from any ﬁle names that occur earlier on the command

line. For example, assume the ﬁle foo contains:

$ cat foo

bar

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GNU M4 macro processor v1.4.18手册

m4.pdf(1.4.16)

GNU Make项目管理.pdf

gnu.io.SerialPort( rxtx-2.1.7.jar)

/usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/scrt1.o: in function `_start': (.text+0x20): undefined reference to `main' collect2: error: ld returned 1 exit status

/usr/bin/ld: /usr/lib/gcc/aarch64-linux-gnu/10/../../../aarch64-linux-gnu/libmali.so: .dynsym local symbol at index 3 (>= sh_info of 3) /usr/bin/ld: /usr/lib/gcc/aarch64-linux-gnu/10/../../../aarch64-linux-gnu/libmali.so: .dynsym local symbol at index 4 (>= sh_info of 3)

minicom: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.33' not found (required by /lib/x86_64-linux-gnu/libtinfo.so.6)

ignoring nonexistent directory "/usr/lib/gcc/x86_64-linux-gnu/5/../../../../x86_64-linux-gnu/include"

rk3588 debian11编译opencv-4.5.1调用opencl mali，编译出现错误/usr/bin/ld: /usr/lib/gcc/aarch64-linux-gnu/10/../../../aarch64-linux-gnu/libmali.so.1: .dynsym local symbol at index 3 (>= sh_info of 3)

ln -s /usr/lib/aarch64-linux-gnu/libodbcinst.so.2.0.0 /usr/lib/aarch64-linux-gnu/libodbcinst.so

sudo ln -s /usr/lib/x86_64-linux-gnu/libmpfr.so.6 /usr/lib/x86_64-linux-gnu/libmpfr.so.4

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