1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
|
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE html
PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<meta name="AUTHOR" content="pme@gcc.gnu.org (Phil Edwards)" />
<meta name="KEYWORDS" content="libstdc++, libstdc++, GCC, g++" />
<meta name="DESCRIPTION" content="Configuration options for libstdc++." />
<meta name="GENERATOR" content="vi and eight fingers" />
<title>libstdc++ configure options</title>
<link rel="StyleSheet" href="lib3styles.css" type="text/css" />
<link rel="Copyright" href="17_intro/license.html" type="text/html" />
</head>
<body>
<h1 class="centered"><a name="top">Interesting <code>configure</code>
options</a></h1>
<p class="fineprint"><em>
The latest version of this document is always available at
<a href="http://gcc.gnu.org/onlinedocs/libstdc++/configopts.html">
http://gcc.gnu.org/onlinedocs/libstdc++/configopts.html</a>.
</em></p>
<p><em>
To the <a href="http://gcc.gnu.org/libstdc++/">libstdc++ homepage</a>.
</em></p>
<!-- ####################################################### -->
<hr />
<p>Here are some of the non-obvious options to libstdc++'s configure.
Keep in mind that
<!-- This SECnn should be the "Choosing Package Options" section. -->
<a href="http://www.gnu.org/software/autoconf/manual/autoconf-2.57/html_node/autoconf_131.html#SEC131">they
all have opposite forms as well</a>
(enable/disable and with/without). The defaults are for <strong>current
development sources</strong>, which may be different than those for
released versions.
</p>
<p>The canonical way to find out the configure options that are
available for a given set of libstdc++ sources is to go to the
source directory and then type:<code> ./configure --help</code>
</p>
<dl>
<dt><code>--enable-multilib </code>[default]</dt>
<dd><p>This is part of the generic multilib support for building cross
compilers. As such, targets like "powerpc-elf" will have
libstdc++ built many different ways: "-msoft-float"
and not, etc. A different libstdc++ will be built for each of
the different multilib versions. This option is on by default.
</p>
</dd>
<dt><code>--enable-sjlj-exceptions </code></dt>
<dd><p>Forces old, set-jump/long-jump exception handling model. If
at all possible, the new, frame unwinding exception handling routines
should be used instead, as they significantly reduce both
runtime memory usage and executable size. This option can
change the library ABI.
</p>
</dd>
<dt><code>--enable-version-specific-runtime-libs </code></dt>
<dd><p>Specify that run-time libraries should be installed in the
compiler-specific subdirectory (i.e.,
<code>${libdir}/gcc-lib/${target_alias}/${gcc_version}</code>)
instead of <code>${libdir}</code>. This option is useful if you
intend to use several versions of gcc in parallel. In addition,
libstdc++'s include files will be installed in
<code>${libdir}/gcc-lib/${target_alias}/${gcc_version}/include/g++</code>,
unless you also specify
<code>--with-gxx-include-dir=<em>dirname</em></code> during configuration.
</p>
</dd>
<dt><code>--with-gxx-include-dir=<include-files dir></code></dt>
<dd><p>Adds support for named libstdc++ include directory. For instance,
the following puts all the libstdc++ headers into a directory
called "2.97-20001008" instead of the usual
"c++/(version)".
</p>
<pre>
--with-gxx-include-dir=/foo/H-x86-gcc-3-c-gxx-inc/include/2.97-20001008</pre> </dd>
<dt><code>--enable-cstdio </code></dt>
<dd><p>This is an abbreviated form of <code>'--enable-cstdio=stdio'</code>
(described next). This option can change the library ABI.
</p>
</dd>
<dt><code>--enable-cstdio=OPTION </code></dt>
<dd><p>Select a target-specific I/O package. At the moment, the only
choice is to use 'stdio', a generic "C" abstraction.
The default is 'stdio'.
</p>
</dd>
<dt><code>--enable-clocale </code></dt>
<dd><p>This is an abbreviated form of <code>'--enable-clocale=generic'</code>
(described next). This option can change the library ABI.
</p>
</dd>
<dt><code>--enable-clocale=OPTION </code></dt>
<dd><p>Select a target-specific underlying locale package. The
choices are 'ieee_1003.1-2001' to specify an X/Open, Standard Unix
(IEEE Std. 1003.1-2001) model based on langinfo/iconv/catgets,
'gnu' to specify a model based on functionality from the GNU C
library (langinfo/iconv/gettext) (from <a
href="http://sources.redhat.com/glibc/">glibc</a>, the GNU C
library), or 'generic' to use a generic "C"
abstraction which consists of "C" locale info.
</p>
<p>As part of the configuration process, the "C" library is
probed both for sufficient vintage, and installed locale
data. If either of these elements are not present, the C++
locale model default to 'generic.' On glibc-based systems of
version 2.2.5 and above with installed locale files, 'gnu' is
automatically selected.
</p>
</dd>
<dt><code>--enable-libstdcxx-allocator </code></dt>
<dd><p>This is an abbreviated form of
<code>'--enable-libstdcxx-allocator=auto'</code> (described
next). This option can change the library ABI.
</p>
</dd>
<dt><code>--enable-libstdcxx-allocator=OPTION </code></dt>
<dd><p>Select a target-specific underlying std::allocator. The
choices are 'new' to specify a wrapper for new, 'malloc' to
specify a wrapper for malloc, 'mt' for a fixed power of two allocator
(<a href="ext/mt_allocator.html">documented</a> under extensions),
'pool' for the SGI pooled allocator or 'bitmap' for a bitmap allocator.
This option can change the library ABI.
</p>
</dd>
<dt><code>--enable-cheaders=OPTION </code></dt>
<dd><p>This allows the user to define the approach taken for C header
compatibility with C++. Options are c, c_std, and c_global.
These correspond to the source directory's include/c,
include/c_std, and include/c_global, and may also include
include/c_compatibility. The default is c_global.
</p>
</dd>
<dt><code>--enable-threads </code></dt>
<dd><p>This is an abbreviated form of <code>'--enable-threads=yes'</code>
(described next). This option can change the library ABI.
</p>
</dd>
<dt><code>--enable-threads=OPTION </code></dt>
<dd><p>Select a threading library. A full description is given in the
general <a href="http://gcc.gnu.org/install/configure.html">compiler
configuration instructions</a>.
</p>
</dd>
<dt><code>--enable-libstdcxx-debug </code></dt>
<dd><p>Build separate debug libraries in addition to what is normally built.
By default, the debug libraries are compiled with
<code> CXXFLAGS='-g3 -O0'</code>
, are installed in <code>${libdir}/debug</code>, and have the
same names and versioning information as the non-debug
libraries. This option is off by default.
</p>
<p>Note this make command, executed in
the build directory, will do much the same thing, without the
configuration difference and without building everything twice:
<code>make CXXFLAGS='-g3 -O0' all</code>
</p>
</dd>
<dt><code>--enable-libstdcxx-debug-flags=FLAGS</code></dt>
<dd><p>This option is only valid when <code> --enable-debug </code>
is also specified, and applies to the debug builds only. With
this option, you can pass a specific string of flags to the
compiler to use when building the debug versions of libstdc++.
FLAGS is a quoted string of options, like
</p>
<pre>
--enable-libstdcxx-debug-flags='-g3 -O1 -gdwarf-2'</pre>
</dd>
<dt><code>--enable-cxx-flags=FLAGS</code></dt>
<dd><p>With this option, you can pass a string of -f (functionality)
flags to the compiler to use when building libstdc++. This
option can change the library ABI. FLAGS is a quoted string of
options, like
</p>
<pre>
--enable-cxx-flags='-fvtable-gc -fomit-frame-pointer -ansi'</pre>
<p>
Note that the flags don't necessarily have to all be -f flags,
as shown, but usually those are the ones that will make sense
for experimentation and configure-time overriding.
</p>
<p>The advantage of --enable-cxx-flags over setting CXXFLAGS in
the 'make' environment is that, if files are automatically
rebuilt, the same flags will be used when compiling those files
as well, so that everything matches.
</p>
<p>Fun flags to try might include combinations of
</p>
<pre>
-fstrict-aliasing
-fno-exceptions
-ffunction-sections
-fvtable-gc</pre>
<p>and opposite forms (-fno-) of the same. Tell us (the libstdc++
mailing list) if you discover more!
</p>
</dd>
<dt><code>--enable-c99 </code></dt>
<dd><p>The "long long" type was introduced in C99, along
with many other functions for wide characters, and math
classification macros, etc. If enabled, all C99 functions not
specified by the C++ standard will be put into <code>namespace
__gnu_cxx</code>, and then all these names will
be injected into namespace std, so that C99 functions can be
used "as if" they were in the C++ standard (as they
will eventually be in some future revision of the standard,
without a doubt). By default, C99 support is on, assuming the
configure probes find all the necessary functions and bits
necessary. This option can change the library ABI.
</p>
</dd>
<dt><code>--enable-wchar_t </code>[default]</dt>
<dd><p>Template specializations for the "wchar_t" type are
required for wide character conversion support. Disabling
wide character specializations may be expedient for initial
porting efforts, but builds only a subset of what is required by
ISO, and is not recommended. By default, this option is on.
This option can change the library ABI.
</p>
</dd>
<dt><code>--enable-long-long </code></dt>
<dd><p>The "long long" type was introduced in C99. It is
provided as a GNU extension to C++98 in g++. This flag builds
support for "long long" into the library (specialized
templates and the like for iostreams). This option is on by default:
if enabled, users will have to either use the new-style "C"
headers by default (i.e., <cmath> not <math.h>)
or add appropriate compile-time flags to all compile lines to
allow "C" visibility of this feature (on GNU/Linux,
the flag is -D_ISOC99_SOURCE, which is added automatically via
CPLUSPLUS_CPP_SPEC's addition of _GNU_SOURCE).
This option can change the library ABI.
</p>
</dd>
<dt><code>--enable-fully-dynamic-string </code></dt>
<dd><p>This option enables a special version of basic_string avoiding
the optimization that allocates empty objects in static memory.
Mostly useful together with shared memory allocators, see PR
libstdc++/16612 for details.
</p>
</dd>
<dt><code>--enable-concept-checks </code></dt>
<dd><p>This turns on additional compile-time checks for instantiated
library templates, in the form of specialized templates,
<a href="19_diagnostics/howto.html#3">described here</a>. They
can help users discover when they break the rules of the STL, before
their programs run.
</p>
</dd>
<dt><code>--enable-symvers[=style] </code></dt>
<dd><p>In 3.1 and later, tries to turn on symbol versioning in the
shared library (if a shared library has been
requested). Values for 'style' that are currently supported
are 'gnu', 'gnu-versioned-namespace', 'darwin', and
'darwin-export'. Both gnu- options require that a recent
version of the GNU linker be in use. Both darwin options are
equivalent. With no style given, the configure script will try
to guess correct defaults for the host system, probe to see if
additional requirements are necessary and present for
activation, and if so, will turn symbol versioning on. This
option can change the library ABI.
</p>
</dd>
<dt><code>--enable-visibility </code></dt>
<dd><p> In 4.2 and later, enables or disables visibility attributes.
If enabled (as by default), and the compiler seems capable of
passing the simple sanity checks thrown at it, adjusts items
in namespace std, namespace std::tr1, and namespace __gnu_cxx
so that -fvisibility options work.
</p>
</dd>
<dt><code>--enable-libstdcxx-pch </code></dt>
<dd><p>In 3.4 and later, tries to turn on the generation of
stdc++.h.gch, a pre-compiled file including all the standard
C++ includes. If enabled (as by default), and the compiler
seems capable of passing the simple sanity checks thrown at
it, try to build stdc++.h.gch as part of the make process.
In addition, this generated file is used later on (by appending <code>
--include bits/stdc++.h </code> to CXXFLAGS) when running the
testsuite.
</p>
</dd>
<dt><code>--disable-hosted-libstdcxx </code></dt>
<dd><p>By default, a complete <em>hosted</em> C++ library is built. The
C++ Standard also describes a <em>freestanding</em> environment,
in which only a minimal set of headers are provided. This option
builds such an environment.
</p>
</dd>
</dl>
<p>Return <a href="#top">to the top of the page</a> or
<a href="http://gcc.gnu.org/libstdc++/">to the libstdc++ homepage</a>.
</p>
<!-- ####################################################### -->
<hr />
<p class="fineprint"><em>
See <a href="17_intro/license.html">license.html</a> for copying conditions.
Comments and suggestions are welcome, and may be sent to
<a href="mailto:libstdc++@gcc.gnu.org">the libstdc++ mailing list</a>.
</em></p>
</body>
</html>
|
