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| <div class="header"> |
| <p> |
| Next: <a href="Function-Properties.html#Function-Properties" accesskey="n" rel="next">Function Properties</a>, Up: <a href="Functions.html#Functions" accesskey="u" rel="up">Functions</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="Function-Basics-1"></a> |
| <h4 class="subsection">10.8.1 Function Basics</h4> |
| <a name="index-DECL_005fNAME-1"></a> |
| <a name="index-DECL_005fASSEMBLER_005fNAME"></a> |
| <a name="index-TREE_005fPUBLIC"></a> |
| <a name="index-DECL_005fARTIFICIAL-1"></a> |
| <a name="index-DECL_005fFUNCTION_005fSPECIFIC_005fTARGET"></a> |
| <a name="index-DECL_005fFUNCTION_005fSPECIFIC_005fOPTIMIZATION"></a> |
| |
| <p>A function has four core parts: the name, the parameters, the result, |
| and the body. The following macros and functions access these parts |
| of a <code>FUNCTION_DECL</code> as well as other basic features: |
| </p><dl compact="compact"> |
| <dt><code>DECL_NAME</code> |
| <a name="index-DECL_005fNAME-2"></a> |
| </dt> |
| <dd><p>This macro returns the unqualified name of the function, as an |
| <code>IDENTIFIER_NODE</code>. For an instantiation of a function template, |
| the <code>DECL_NAME</code> is the unqualified name of the template, not |
| something like <code>f<int></code>. The value of <code>DECL_NAME</code> is |
| undefined when used on a constructor, destructor, overloaded operator, |
| or type-conversion operator, or any function that is implicitly |
| generated by the compiler. See below for macros that can be used to |
| distinguish these cases. |
| </p> |
| </dd> |
| <dt><code>DECL_ASSEMBLER_NAME</code> |
| <a name="index-DECL_005fASSEMBLER_005fNAME-1"></a> |
| </dt> |
| <dd><p>This macro returns the mangled name of the function, also an |
| <code>IDENTIFIER_NODE</code>. This name does not contain leading underscores |
| on systems that prefix all identifiers with underscores. The mangled |
| name is computed in the same way on all platforms; if special processing |
| is required to deal with the object file format used on a particular |
| platform, it is the responsibility of the back end to perform those |
| modifications. (Of course, the back end should not modify |
| <code>DECL_ASSEMBLER_NAME</code> itself.) |
| </p> |
| <p>Using <code>DECL_ASSEMBLER_NAME</code> will cause additional memory to be |
| allocated (for the mangled name of the entity) so it should be used |
| only when emitting assembly code. It should not be used within the |
| optimizers to determine whether or not two declarations are the same, |
| even though some of the existing optimizers do use it in that way. |
| These uses will be removed over time. |
| </p> |
| </dd> |
| <dt><code>DECL_ARGUMENTS</code> |
| <a name="index-DECL_005fARGUMENTS"></a> |
| </dt> |
| <dd><p>This macro returns the <code>PARM_DECL</code> for the first argument to the |
| function. Subsequent <code>PARM_DECL</code> nodes can be obtained by |
| following the <code>TREE_CHAIN</code> links. |
| </p> |
| </dd> |
| <dt><code>DECL_RESULT</code> |
| <a name="index-DECL_005fRESULT"></a> |
| </dt> |
| <dd><p>This macro returns the <code>RESULT_DECL</code> for the function. |
| </p> |
| </dd> |
| <dt><code>DECL_SAVED_TREE</code> |
| <a name="index-DECL_005fSAVED_005fTREE"></a> |
| </dt> |
| <dd><p>This macro returns the complete body of the function. |
| </p> |
| </dd> |
| <dt><code>TREE_TYPE</code> |
| <a name="index-TREE_005fTYPE-5"></a> |
| </dt> |
| <dd><p>This macro returns the <code>FUNCTION_TYPE</code> or <code>METHOD_TYPE</code> for |
| the function. |
| </p> |
| </dd> |
| <dt><code>DECL_INITIAL</code> |
| <a name="index-DECL_005fINITIAL-1"></a> |
| </dt> |
| <dd><p>A function that has a definition in the current translation unit will |
| have a non-<code>NULL</code> <code>DECL_INITIAL</code>. However, back ends should not make |
| use of the particular value given by <code>DECL_INITIAL</code>. |
| </p> |
| <p>It should contain a tree of <code>BLOCK</code> nodes that mirrors the scopes |
| that variables are bound in the function. Each block contains a list |
| of decls declared in a basic block, a pointer to a chain of blocks at |
| the next lower scope level, then a pointer to the next block at the |
| same level and a backpointer to the parent <code>BLOCK</code> or |
| <code>FUNCTION_DECL</code>. So given a function as follows: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">void foo() |
| { |
| int a; |
| { |
| int b; |
| } |
| int c; |
| } |
| </pre></div> |
| |
| <p>you would get the following: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">tree foo = FUNCTION_DECL; |
| tree decl_a = VAR_DECL; |
| tree decl_b = VAR_DECL; |
| tree decl_c = VAR_DECL; |
| tree block_a = BLOCK; |
| tree block_b = BLOCK; |
| tree block_c = BLOCK; |
| BLOCK_VARS(block_a) = decl_a; |
| BLOCK_SUBBLOCKS(block_a) = block_b; |
| BLOCK_CHAIN(block_a) = block_c; |
| BLOCK_SUPERCONTEXT(block_a) = foo; |
| BLOCK_VARS(block_b) = decl_b; |
| BLOCK_SUPERCONTEXT(block_b) = block_a; |
| BLOCK_VARS(block_c) = decl_c; |
| BLOCK_SUPERCONTEXT(block_c) = foo; |
| DECL_INITIAL(foo) = block_a; |
| </pre></div> |
| |
| </dd> |
| </dl> |
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