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| <a name="Uninitialized-Data"></a> |
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| Next: <a href="Label-Output.html#Label-Output" accesskey="n" rel="next">Label Output</a>, Previous: <a href="Data-Output.html#Data-Output" accesskey="p" rel="prev">Data Output</a>, Up: <a href="Assembler-Format.html#Assembler-Format" accesskey="u" rel="up">Assembler Format</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p> |
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| <a name="Output-of-Uninitialized-Variables"></a> |
| <h4 class="subsection">17.21.3 Output of Uninitialized Variables</h4> |
| |
| <p>Each of the macros in this section is used to do the whole job of |
| outputting a single uninitialized variable. |
| </p> |
| <dl> |
| <dt><a name="index-ASM_005fOUTPUT_005fCOMMON"></a>Macro: <strong>ASM_OUTPUT_COMMON</strong> <em>(<var>stream</var>, <var>name</var>, <var>size</var>, <var>rounded</var>)</em></dt> |
| <dd><p>A C statement (sans semicolon) to output to the stdio stream |
| <var>stream</var> the assembler definition of a common-label named |
| <var>name</var> whose size is <var>size</var> bytes. The variable <var>rounded</var> |
| is the size rounded up to whatever alignment the caller wants. It is |
| possible that <var>size</var> may be zero, for instance if a struct with no |
| other member than a zero-length array is defined. In this case, the |
| backend must output a symbol definition that allocates at least one |
| byte, both so that the address of the resulting object does not compare |
| equal to any other, and because some object formats cannot even express |
| the concept of a zero-sized common symbol, as that is how they represent |
| an ordinary undefined external. |
| </p> |
| <p>Use the expression <code>assemble_name (<var>stream</var>, <var>name</var>)</code> to |
| output the name itself; before and after that, output the additional |
| assembler syntax for defining the name, and a newline. |
| </p> |
| <p>This macro controls how the assembler definitions of uninitialized |
| common global variables are output. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-ASM_005fOUTPUT_005fALIGNED_005fCOMMON"></a>Macro: <strong>ASM_OUTPUT_ALIGNED_COMMON</strong> <em>(<var>stream</var>, <var>name</var>, <var>size</var>, <var>alignment</var>)</em></dt> |
| <dd><p>Like <code>ASM_OUTPUT_COMMON</code> except takes the required alignment as a |
| separate, explicit argument. If you define this macro, it is used in |
| place of <code>ASM_OUTPUT_COMMON</code>, and gives you more flexibility in |
| handling the required alignment of the variable. The alignment is specified |
| as the number of bits. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-ASM_005fOUTPUT_005fALIGNED_005fDECL_005fCOMMON"></a>Macro: <strong>ASM_OUTPUT_ALIGNED_DECL_COMMON</strong> <em>(<var>stream</var>, <var>decl</var>, <var>name</var>, <var>size</var>, <var>alignment</var>)</em></dt> |
| <dd><p>Like <code>ASM_OUTPUT_ALIGNED_COMMON</code> except that <var>decl</var> of the |
| variable to be output, if there is one, or <code>NULL_TREE</code> if there |
| is no corresponding variable. If you define this macro, GCC will use it |
| in place of both <code>ASM_OUTPUT_COMMON</code> and |
| <code>ASM_OUTPUT_ALIGNED_COMMON</code>. Define this macro when you need to see |
| the variable’s decl in order to chose what to output. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-ASM_005fOUTPUT_005fALIGNED_005fBSS"></a>Macro: <strong>ASM_OUTPUT_ALIGNED_BSS</strong> <em>(<var>stream</var>, <var>decl</var>, <var>name</var>, <var>size</var>, <var>alignment</var>)</em></dt> |
| <dd><p>A C statement (sans semicolon) to output to the stdio stream |
| <var>stream</var> the assembler definition of uninitialized global <var>decl</var> named |
| <var>name</var> whose size is <var>size</var> bytes. The variable <var>alignment</var> |
| is the alignment specified as the number of bits. |
| </p> |
| <p>Try to use function <code>asm_output_aligned_bss</code> defined in file |
| <samp>varasm.c</samp> when defining this macro. If unable, use the expression |
| <code>assemble_name (<var>stream</var>, <var>name</var>)</code> to output the name itself; |
| before and after that, output the additional assembler syntax for defining |
| the name, and a newline. |
| </p> |
| <p>There are two ways of handling global BSS. One is to define this macro. |
| The other is to have <code>TARGET_ASM_SELECT_SECTION</code> return a |
| switchable BSS section (see <a href="File-Framework.html#TARGET_005fHAVE_005fSWITCHABLE_005fBSS_005fSECTIONS">TARGET_HAVE_SWITCHABLE_BSS_SECTIONS</a>). |
| You do not need to do both. |
| </p> |
| <p>Some languages do not have <code>common</code> data, and require a |
| non-common form of global BSS in order to handle uninitialized globals |
| efficiently. C++ is one example of this. However, if the target does |
| not support global BSS, the front end may choose to make globals |
| common in order to save space in the object file. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-ASM_005fOUTPUT_005fLOCAL"></a>Macro: <strong>ASM_OUTPUT_LOCAL</strong> <em>(<var>stream</var>, <var>name</var>, <var>size</var>, <var>rounded</var>)</em></dt> |
| <dd><p>A C statement (sans semicolon) to output to the stdio stream |
| <var>stream</var> the assembler definition of a local-common-label named |
| <var>name</var> whose size is <var>size</var> bytes. The variable <var>rounded</var> |
| is the size rounded up to whatever alignment the caller wants. |
| </p> |
| <p>Use the expression <code>assemble_name (<var>stream</var>, <var>name</var>)</code> to |
| output the name itself; before and after that, output the additional |
| assembler syntax for defining the name, and a newline. |
| </p> |
| <p>This macro controls how the assembler definitions of uninitialized |
| static variables are output. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-ASM_005fOUTPUT_005fALIGNED_005fLOCAL"></a>Macro: <strong>ASM_OUTPUT_ALIGNED_LOCAL</strong> <em>(<var>stream</var>, <var>name</var>, <var>size</var>, <var>alignment</var>)</em></dt> |
| <dd><p>Like <code>ASM_OUTPUT_LOCAL</code> except takes the required alignment as a |
| separate, explicit argument. If you define this macro, it is used in |
| place of <code>ASM_OUTPUT_LOCAL</code>, and gives you more flexibility in |
| handling the required alignment of the variable. The alignment is specified |
| as the number of bits. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-ASM_005fOUTPUT_005fALIGNED_005fDECL_005fLOCAL"></a>Macro: <strong>ASM_OUTPUT_ALIGNED_DECL_LOCAL</strong> <em>(<var>stream</var>, <var>decl</var>, <var>name</var>, <var>size</var>, <var>alignment</var>)</em></dt> |
| <dd><p>Like <code>ASM_OUTPUT_ALIGNED_DECL</code> except that <var>decl</var> of the |
| variable to be output, if there is one, or <code>NULL_TREE</code> if there |
| is no corresponding variable. If you define this macro, GCC will use it |
| in place of both <code>ASM_OUTPUT_DECL</code> and |
| <code>ASM_OUTPUT_ALIGNED_DECL</code>. Define this macro when you need to see |
| the variable’s decl in order to chose what to output. |
| </p></dd></dl> |
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| Next: <a href="Label-Output.html#Label-Output" accesskey="n" rel="next">Label Output</a>, Previous: <a href="Data-Output.html#Data-Output" accesskey="p" rel="prev">Data Output</a>, Up: <a href="Assembler-Format.html#Assembler-Format" accesskey="u" rel="up">Assembler Format</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p> |
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