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| <title>LD: Environment</title> |
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| <a name="Environment-Variables"></a> |
| <h3 class="section">2.2 Environment Variables</h3> |
| |
| |
| <p>You can change the behaviour of <code>ld</code> with the environment variables |
| <code>GNUTARGET</code>, |
| <code>LDEMULATION</code> and <code>COLLECT_NO_DEMANGLE</code>. |
| </p> |
| <a name="index-GNUTARGET"></a> |
| <a name="index-default-input-format"></a> |
| <p><code>GNUTARGET</code> determines the input-file object format if you don’t |
| use ‘<samp>-b</samp>’ (or its synonym ‘<samp>--format</samp>’). Its value should be one |
| of the BFD names for an input format (see <a href="BFD.html#BFD">BFD</a>). If there is no |
| <code>GNUTARGET</code> in the environment, <code>ld</code> uses the natural format |
| of the target. If <code>GNUTARGET</code> is set to <code>default</code> then BFD |
| attempts to discover the input format by examining binary input files; |
| this method often succeeds, but there are potential ambiguities, since |
| there is no method of ensuring that the magic number used to specify |
| object-file formats is unique. However, the configuration procedure for |
| BFD on each system places the conventional format for that system first |
| in the search-list, so ambiguities are resolved in favor of convention. |
| </p> |
| <a name="index-LDEMULATION"></a> |
| <a name="index-default-emulation"></a> |
| <a name="index-emulation_002c-default"></a> |
| <p><code>LDEMULATION</code> determines the default emulation if you don’t use the |
| ‘<samp>-m</samp>’ option. The emulation can affect various aspects of linker |
| behaviour, particularly the default linker script. You can list the |
| available emulations with the ‘<samp>--verbose</samp>’ or ‘<samp>-V</samp>’ options. If |
| the ‘<samp>-m</samp>’ option is not used, and the <code>LDEMULATION</code> environment |
| variable is not defined, the default emulation depends upon how the |
| linker was configured. |
| </p> |
| <a name="index-COLLECT_005fNO_005fDEMANGLE"></a> |
| <a name="index-demangling_002c-default"></a> |
| <p>Normally, the linker will default to demangling symbols. However, if |
| <code>COLLECT_NO_DEMANGLE</code> is set in the environment, then it will |
| default to not demangling symbols. This environment variable is used in |
| a similar fashion by the <code>gcc</code> linker wrapper program. The default |
| may be overridden by the ‘<samp>--demangle</samp>’ and ‘<samp>--no-demangle</samp>’ |
| options. |
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