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22 | <a href="./Home">MLton 20180207</a>\r | |
23 | </div>\r | |
24 | </div>\r | |
25 | <div id="header">\r | |
26 | <h1>CallingFromSMLToCFunctionPointer</h1>\r | |
27 | </div>\r | |
28 | <div id="content">\r | |
29 | <div id="preamble">\r | |
30 | <div class="sectionbody">\r | |
31 | <div class="paragraph"><p>Just as MLton can <a href="CallingFromSMLToC">directly call C functions</a>, it\r | |
32 | is possible to make indirect function calls; that is, function calls\r | |
33 | through a function pointer. MLton extends the syntax of SML to allow\r | |
34 | expressions like the following:</p></div>\r | |
35 | <div class="listingblock">\r | |
36 | <div class="content monospaced">\r | |
37 | <pre>_import * : MLton.Pointer.t -> real * char -> int;</pre>\r | |
38 | </div></div>\r | |
39 | <div class="paragraph"><p>This expression denotes a function of type</p></div>\r | |
40 | <div class="listingblock">\r | |
41 | <div class="content"><div class="highlight"><pre><span class="n">MLton</span><span class="p">.</span><span class="n">Pointer</span><span class="p">.</span><span class="n">t</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">real</span><span class="w"> </span><span class="n">*</span><span class="w"> </span><span class="n">char</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">int</span><span class="w"></span>\r | |
42 | </pre></div></div></div>\r | |
43 | <div class="paragraph"><p>whose behavior is implemented by calling the C function at the address\r | |
44 | denoted by the <span class="monospaced">MLton.Pointer.t</span> argument, and supplying the C\r | |
45 | function two arguments, a <span class="monospaced">double</span> and an <span class="monospaced">int</span>. The C function\r | |
46 | pointer may be obtained, for example, by the dynamic linking loader\r | |
47 | (<span class="monospaced">dlopen</span>, <span class="monospaced">dlsym</span>, …).</p></div>\r | |
48 | <div class="paragraph"><p>The general form of an indirect <span class="monospaced">_import</span> expression is:</p></div>\r | |
49 | <div class="listingblock">\r | |
50 | <div class="content monospaced">\r | |
51 | <pre>_import * attr... : cPtrTy -> cFuncTy;</pre>\r | |
52 | </div></div>\r | |
53 | <div class="paragraph"><p>The type and the semicolon are not optional.</p></div>\r | |
54 | </div>\r | |
55 | </div>\r | |
56 | <div class="sect1">\r | |
57 | <h2 id="_example">Example</h2>\r | |
58 | <div class="sectionbody">\r | |
59 | <div class="paragraph"><p>This example uses <span class="monospaced">dlopen</span> and friends (imported using normal\r | |
60 | <span class="monospaced">_import</span>) to dynamically load the math library (<span class="monospaced">libm</span>) and call the\r | |
61 | <span class="monospaced">cos</span> function. Suppose <span class="monospaced">iimport.sml</span> contains the following.</p></div>\r | |
62 | <div class="listingblock">\r | |
63 | <div class="content"><div class="highlight"><pre><span class="k">signature</span><span class="w"> </span><span class="n">DYN_LINK</span><span class="w"> </span><span class="p">=</span><span class="w"></span>\r | |
64 | <span class="w"> </span><span class="k">sig</span><span class="w"></span>\r | |
65 | <span class="w"> </span><span class="k">type</span><span class="w"> </span><span class="n">hndl</span><span class="w"></span>\r | |
66 | <span class="w"> </span><span class="k">type</span><span class="w"> </span><span class="n">mode</span><span class="w"></span>\r | |
67 | <span class="w"> </span><span class="k">type</span><span class="w"> </span><span class="n">fptr</span><span class="w"></span>\r | |
68 | \r | |
69 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">dlopen</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="n">*</span><span class="w"> </span><span class="n">mode</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">hndl</span><span class="w"></span>\r | |
70 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">dlsym</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">hndl</span><span class="w"> </span><span class="n">*</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">fptr</span><span class="w"></span>\r | |
71 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">dlclose</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">hndl</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">unit</span><span class="w"></span>\r | |
72 | \r | |
73 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">RTLD_LAZY</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">mode</span><span class="w"></span>\r | |
74 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">RTLD_NOW</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">mode</span><span class="w"></span>\r | |
75 | <span class="w"> </span><span class="k">end</span><span class="w"></span>\r | |
76 | \r | |
77 | <span class="k">structure</span><span class="w"> </span><span class="n">DynLink</span><span class="w"> </span><span class="p">:></span><span class="w"> </span><span class="n">DYN_LINK</span><span class="w"> </span><span class="p">=</span><span class="w"></span>\r | |
78 | <span class="w"> </span><span class="k">struct</span><span class="w"></span>\r | |
79 | <span class="w"> </span><span class="k">type</span><span class="w"> </span><span class="n">hndl</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="n">MLton</span><span class="p">.</span><span class="n">Pointer</span><span class="p">.</span><span class="n">t</span><span class="w"></span>\r | |
80 | <span class="w"> </span><span class="k">type</span><span class="w"> </span><span class="n">mode</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="n">Word32</span><span class="p">.</span><span class="n">word</span><span class="w"></span>\r | |
81 | <span class="w"> </span><span class="k">type</span><span class="w"> </span><span class="n">fptr</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="n">MLton</span><span class="p">.</span><span class="n">Pointer</span><span class="p">.</span><span class="n">t</span><span class="w"></span>\r | |
82 | \r | |
83 | <span class="w"> </span><span class="cm">(* These symbols come from a system libray, so the default import scope</span>\r | |
84 | <span class="cm"> * of external is correct.</span>\r | |
85 | <span class="cm"> *)</span><span class="w"></span>\r | |
86 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">dlopen</span><span class="w"> </span><span class="p">=</span><span class="w"></span>\r | |
87 | <span class="w"> </span><span class="p">_</span><span class="n">import</span><span class="w"> </span><span class="s">"dlopen"</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="n">*</span><span class="w"> </span><span class="n">mode</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">hndl</span><span class="p">;</span><span class="w"></span>\r | |
88 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">dlerror</span><span class="w"> </span><span class="p">=</span><span class="w"></span>\r | |
89 | <span class="w"> </span><span class="p">_</span><span class="n">import</span><span class="w"> </span><span class="s">"dlerror"</span><span class="p">:</span><span class="w"> </span><span class="n">unit</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">MLton</span><span class="p">.</span><span class="n">Pointer</span><span class="p">.</span><span class="n">t</span><span class="p">;</span><span class="w"></span>\r | |
90 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">dlsym</span><span class="w"> </span><span class="p">=</span><span class="w"></span>\r | |
91 | <span class="w"> </span><span class="p">_</span><span class="n">import</span><span class="w"> </span><span class="s">"dlsym"</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">hndl</span><span class="w"> </span><span class="n">*</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">fptr</span><span class="p">;</span><span class="w"></span>\r | |
92 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">dlclose</span><span class="w"> </span><span class="p">=</span><span class="w"></span>\r | |
93 | <span class="w"> </span><span class="p">_</span><span class="n">import</span><span class="w"> </span><span class="s">"dlclose"</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">hndl</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">Int32</span><span class="p">.</span><span class="n">int</span><span class="p">;</span><span class="w"></span>\r | |
94 | \r | |
95 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">RTLD_LAZY</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="mh">0wx00001</span><span class="w"> </span><span class="cm">(* Lazy function call binding. *)</span><span class="w"></span>\r | |
96 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">RTLD_NOW</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="mh">0wx00002</span><span class="w"> </span><span class="cm">(* Immediate function call binding. *)</span><span class="w"></span>\r | |
97 | \r | |
98 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">dlerror</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="k">fn</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="p">=></span><span class="w"></span>\r | |
99 | <span class="w"> </span><span class="k">let</span><span class="w"></span>\r | |
100 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">addr</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="n">dlerror</span><span class="w"> </span><span class="p">()</span><span class="w"></span>\r | |
101 | <span class="w"> </span><span class="k">in</span><span class="w"></span>\r | |
102 | <span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="n">addr</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="n">MLton</span><span class="p">.</span><span class="n">Pointer</span><span class="p">.</span><span class="n">null</span><span class="w"></span>\r | |
103 | <span class="w"> </span><span class="k">then</span><span class="w"> </span><span class="n">NONE</span><span class="w"></span>\r | |
104 | <span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">let</span><span class="w"></span>\r | |
105 | <span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="n">loop</span><span class="w"> </span><span class="p">(</span><span class="n">index</span><span class="p">,</span><span class="w"> </span><span class="n">cs</span><span class="p">)</span><span class="w"> </span><span class="p">=</span><span class="w"></span>\r | |
106 | <span class="w"> </span><span class="k">let</span><span class="w"></span>\r | |
107 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">w</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="n">MLton</span><span class="p">.</span><span class="n">Pointer</span><span class="p">.</span><span class="n">getWord8</span><span class="w"> </span><span class="p">(</span><span class="n">addr</span><span class="p">,</span><span class="w"> </span><span class="n">index</span><span class="p">)</span><span class="w"></span>\r | |
108 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">c</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="n">Byte</span><span class="p">.</span><span class="n">byteToChar</span><span class="w"> </span><span class="n">w</span><span class="w"></span>\r | |
109 | <span class="w"> </span><span class="k">in</span><span class="w"></span>\r | |
110 | <span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="n">c</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="p">#</span><span class="s">"</span><span class="se">\000</span><span class="s">"</span><span class="w"></span>\r | |
111 | <span class="w"> </span><span class="k">then</span><span class="w"> </span><span class="n">SOME</span><span class="w"> </span><span class="p">(</span><span class="n">implode</span><span class="w"> </span><span class="p">(</span><span class="n">rev</span><span class="w"> </span><span class="n">cs</span><span class="p">))</span><span class="w"></span>\r | |
112 | <span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="n">loop</span><span class="w"> </span><span class="p">(</span><span class="n">index</span><span class="w"> </span><span class="n">+</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">c::cs</span><span class="p">)</span><span class="w"></span>\r | |
113 | <span class="w"> </span><span class="k">end</span><span class="w"></span>\r | |
114 | <span class="w"> </span><span class="k">in</span><span class="w"></span>\r | |
115 | <span class="w"> </span><span class="n">loop</span><span class="w"> </span><span class="p">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">[])</span><span class="w"></span>\r | |
116 | <span class="w"> </span><span class="k">end</span><span class="w"></span>\r | |
117 | <span class="w"> </span><span class="k">end</span><span class="w"></span>\r | |
118 | \r | |
119 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">dlopen</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="k">fn</span><span class="w"> </span><span class="p">(</span><span class="n">filename</span><span class="p">,</span><span class="w"> </span><span class="n">mode</span><span class="p">)</span><span class="w"> </span><span class="p">=></span><span class="w"></span>\r | |
120 | <span class="w"> </span><span class="k">let</span><span class="w"></span>\r | |
121 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">filename</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="n">filename</span><span class="w"> </span><span class="n">^</span><span class="w"> </span><span class="s">"</span><span class="se">\000</span><span class="s">"</span><span class="w"></span>\r | |
122 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">hndl</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="n">dlopen</span><span class="w"> </span><span class="p">(</span><span class="n">filename</span><span class="p">,</span><span class="w"> </span><span class="n">mode</span><span class="p">)</span><span class="w"></span>\r | |
123 | <span class="w"> </span><span class="k">in</span><span class="w"></span>\r | |
124 | <span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="n">hndl</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="n">MLton</span><span class="p">.</span><span class="n">Pointer</span><span class="p">.</span><span class="n">null</span><span class="w"></span>\r | |
125 | <span class="w"> </span><span class="k">then</span><span class="w"> </span><span class="k">raise</span><span class="w"> </span><span class="n">Fail</span><span class="w"> </span><span class="p">(</span><span class="k">case</span><span class="w"> </span><span class="n">dlerror</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="k">of</span><span class="w"></span>\r | |
126 | <span class="w"> </span><span class="n">NONE</span><span class="w"> </span><span class="p">=></span><span class="w"> </span><span class="s">"???"</span><span class="w"></span>\r | |
127 | <span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">SOME</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="p">=></span><span class="w"> </span><span class="n">s</span><span class="p">)</span><span class="w"></span>\r | |
128 | <span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="n">hndl</span><span class="w"></span>\r | |
129 | <span class="w"> </span><span class="k">end</span><span class="w"></span>\r | |
130 | \r | |
131 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">dlsym</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="k">fn</span><span class="w"> </span><span class="p">(</span><span class="n">hndl</span><span class="p">,</span><span class="w"> </span><span class="n">symbol</span><span class="p">)</span><span class="w"> </span><span class="p">=></span><span class="w"></span>\r | |
132 | <span class="w"> </span><span class="k">let</span><span class="w"></span>\r | |
133 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">symbol</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="n">symbol</span><span class="w"> </span><span class="n">^</span><span class="w"> </span><span class="s">"</span><span class="se">\000</span><span class="s">"</span><span class="w"></span>\r | |
134 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">fptr</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="n">dlsym</span><span class="w"> </span><span class="p">(</span><span class="n">hndl</span><span class="p">,</span><span class="w"> </span><span class="n">symbol</span><span class="p">)</span><span class="w"></span>\r | |
135 | <span class="w"> </span><span class="k">in</span><span class="w"></span>\r | |
136 | <span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="n">dlerror</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="k">of</span><span class="w"></span>\r | |
137 | <span class="w"> </span><span class="n">NONE</span><span class="w"> </span><span class="p">=></span><span class="w"> </span><span class="n">fptr</span><span class="w"></span>\r | |
138 | <span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">SOME</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="p">=></span><span class="w"> </span><span class="k">raise</span><span class="w"> </span><span class="n">Fail</span><span class="w"> </span><span class="n">s</span><span class="w"></span>\r | |
139 | <span class="w"> </span><span class="k">end</span><span class="w"></span>\r | |
140 | \r | |
141 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">dlclose</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="k">fn</span><span class="w"> </span><span class="n">hndl</span><span class="w"> </span><span class="p">=></span><span class="w"></span>\r | |
142 | <span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="n">MLton</span><span class="p">.</span><span class="n">Platform</span><span class="p">.</span><span class="n">OS</span><span class="p">.</span><span class="n">host</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="n">MLton</span><span class="p">.</span><span class="n">Platform</span><span class="p">.</span><span class="n">OS</span><span class="p">.</span><span class="n">Darwin</span><span class="w"></span>\r | |
143 | <span class="w"> </span><span class="k">then</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="cm">(* Darwin reports the following error message if you</span>\r | |
144 | <span class="cm"> * try to close a dynamic library.</span>\r | |
145 | <span class="cm"> * "dynamic libraries cannot be closed"</span>\r | |
146 | <span class="cm"> * So, we disable dlclose on Darwin.</span>\r | |
147 | <span class="cm"> *)</span><span class="w"></span>\r | |
148 | <span class="w"> </span><span class="k">else</span><span class="w"></span>\r | |
149 | <span class="w"> </span><span class="k">let</span><span class="w"></span>\r | |
150 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">res</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="n">dlclose</span><span class="w"> </span><span class="n">hndl</span><span class="w"></span>\r | |
151 | <span class="w"> </span><span class="k">in</span><span class="w"></span>\r | |
152 | <span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="n">res</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="mi">0</span><span class="w"></span>\r | |
153 | <span class="w"> </span><span class="k">then</span><span class="w"> </span><span class="p">()</span><span class="w"></span>\r | |
154 | <span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">raise</span><span class="w"> </span><span class="n">Fail</span><span class="w"> </span><span class="p">(</span><span class="k">case</span><span class="w"> </span><span class="n">dlerror</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="k">of</span><span class="w"></span>\r | |
155 | <span class="w"> </span><span class="n">NONE</span><span class="w"> </span><span class="p">=></span><span class="w"> </span><span class="s">"???"</span><span class="w"></span>\r | |
156 | <span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">SOME</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="p">=></span><span class="w"> </span><span class="n">s</span><span class="p">)</span><span class="w"></span>\r | |
157 | <span class="w"> </span><span class="k">end</span><span class="w"></span>\r | |
158 | <span class="w"> </span><span class="k">end</span><span class="w"></span>\r | |
159 | \r | |
160 | <span class="k">val</span><span class="w"> </span><span class="n">dll</span><span class="w"> </span><span class="p">=</span><span class="w"></span>\r | |
161 | <span class="w"> </span><span class="k">let</span><span class="w"></span>\r | |
162 | <span class="w"> </span><span class="k">open</span><span class="w"> </span><span class="n">MLton</span><span class="p">.</span><span class="n">Platform</span><span class="p">.</span><span class="n">OS</span><span class="w"></span>\r | |
163 | <span class="w"> </span><span class="k">in</span><span class="w"></span>\r | |
164 | <span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="n">host</span><span class="w"> </span><span class="k">of</span><span class="w"></span>\r | |
165 | <span class="w"> </span><span class="n">Cygwin</span><span class="w"> </span><span class="p">=></span><span class="w"> </span><span class="s">"cygwin1.dll"</span><span class="w"></span>\r | |
166 | <span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Darwin</span><span class="w"> </span><span class="p">=></span><span class="w"> </span><span class="s">"libm.dylib"</span><span class="w"></span>\r | |
167 | <span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="p">_</span><span class="w"> </span><span class="p">=></span><span class="w"> </span><span class="s">"libm.so"</span><span class="w"></span>\r | |
168 | <span class="w"> </span><span class="k">end</span><span class="w"></span>\r | |
169 | \r | |
170 | <span class="k">val</span><span class="w"> </span><span class="n">hndl</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="n">DynLink</span><span class="p">.</span><span class="n">dlopen</span><span class="w"> </span><span class="p">(</span><span class="n">dll</span><span class="p">,</span><span class="w"> </span><span class="n">DynLink</span><span class="p">.</span><span class="n">RTLD_LAZY</span><span class="p">)</span><span class="w"></span>\r | |
171 | \r | |
172 | <span class="k">local</span><span class="w"></span>\r | |
173 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">double_to_double</span><span class="w"> </span><span class="p">=</span><span class="w"></span>\r | |
174 | <span class="w"> </span><span class="p">_</span><span class="n">import</span><span class="w"> </span><span class="n">*</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">DynLink</span><span class="p">.</span><span class="n">fptr</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">real</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">real</span><span class="p">;</span><span class="w"></span>\r | |
175 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">cos_fptr</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="n">DynLink</span><span class="p">.</span><span class="n">dlsym</span><span class="w"> </span><span class="p">(</span><span class="n">hndl</span><span class="p">,</span><span class="w"> </span><span class="s">"cos"</span><span class="p">)</span><span class="w"></span>\r | |
176 | <span class="k">in</span><span class="w"></span>\r | |
177 | <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">cos</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="n">double_to_double</span><span class="w"> </span><span class="n">cos_fptr</span><span class="w"></span>\r | |
178 | <span class="k">end</span><span class="w"></span>\r | |
179 | \r | |
180 | <span class="k">val</span><span class="w"> </span><span class="p">_</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="n">print</span><span class="w"> </span><span class="p">(</span><span class="n">concat</span><span class="w"> </span><span class="p">[</span><span class="s">" Math.cos(2.0) = "</span><span class="p">,</span><span class="w"> </span><span class="n">Real</span><span class="p">.</span><span class="n">toString</span><span class="w"> </span><span class="p">(</span><span class="n">Math</span><span class="p">.</span><span class="n">cos</span><span class="w"> </span><span class="mf">2.0</span><span class="p">),</span><span class="w"> </span><span class="s">"</span><span class="se">\n</span><span class="s">"</span><span class="p">,</span><span class="w"></span>\r | |
181 | <span class="w"> </span><span class="s">"libm.so::cos(2.0) = "</span><span class="p">,</span><span class="w"> </span><span class="n">Real</span><span class="p">.</span><span class="n">toString</span><span class="w"> </span><span class="p">(</span><span class="n">cos</span><span class="w"> </span><span class="mf">2.0</span><span class="p">),</span><span class="w"> </span><span class="s">"</span><span class="se">\n</span><span class="s">"</span><span class="p">])</span><span class="w"></span>\r | |
182 | \r | |
183 | <span class="k">val</span><span class="w"> </span><span class="p">_</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="n">DynLink</span><span class="p">.</span><span class="n">dlclose</span><span class="w"> </span><span class="n">hndl</span><span class="w"></span>\r | |
184 | </pre></div></div></div>\r | |
185 | <div class="paragraph"><p>Compile and run <span class="monospaced">iimport.sml</span>.</p></div>\r | |
186 | <div class="listingblock">\r | |
187 | <div class="content monospaced">\r | |
188 | <pre>% mlton -default-ann 'allowFFI true' \\r | |
189 | -target-link-opt linux -ldl \\r | |
190 | -target-link-opt solaris -ldl \\r | |
191 | iimport.sml\r | |
192 | % iimport\r | |
193 | Math.cos(2.0) = ~0.416146836547\r | |
194 | libm.so::cos(2.0) = ~0.416146836547</pre>\r | |
195 | </div></div>\r | |
196 | <div class="paragraph"><p>This example also shows the <span class="monospaced">-target-link-opt</span> option, which uses the\r | |
197 | switch when linking only when on the specified platform. Compile with\r | |
198 | <span class="monospaced">-verbose 1</span> to see in more detail what’s being passed to <span class="monospaced">gcc</span>.</p></div>\r | |
199 | </div>\r | |
200 | </div>\r | |
201 | <div class="sect1">\r | |
202 | <h2 id="_download">Download</h2>\r | |
203 | <div class="sectionbody">\r | |
204 | <div class="ulist"><ul>\r | |
205 | <li>\r | |
206 | <p>\r | |
207 | <a href="https://raw.github.com/MLton/mlton/master/doc/examples/ffi/iimport.sml"><span class="monospaced">iimport.sml</span></a>\r | |
208 | </p>\r | |
209 | </li>\r | |
210 | </ul></div>\r | |
211 | </div>\r | |
212 | </div>\r | |
213 | </div>\r | |
214 | <div id="footnotes"><hr></div>\r | |
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