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<title>The GNU Fortran Compiler: Non-Fortran Main Program</title>
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<a name="Non_002dFortran-Main-Program"></a>
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<p>
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Next: <a href="Naming-and-argument_002dpassing-conventions.html#Naming-and-argument_002dpassing-conventions" accesskey="n" rel="next">Naming and argument-passing conventions</a>, Previous: <a href="GNU-Fortran-Compiler-Directives.html#GNU-Fortran-Compiler-Directives" accesskey="p" rel="prev">GNU Fortran Compiler Directives</a>, Up: <a href="Mixed_002dLanguage-Programming.html#Mixed_002dLanguage-Programming" accesskey="u" rel="up">Mixed-Language Programming</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="Non_002dFortran-Main-Program-1"></a>
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<h3 class="section">7.3 Non-Fortran Main Program</h3>
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<tr><td align="left" valign="top">• <a href="_005fgfortran_005fset_005fargs.html#g_t_005fgfortran_005fset_005fargs" accesskey="1">_gfortran_set_args</a>:</td><td> </td><td align="left" valign="top">Save command-line arguments
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</td></tr>
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<tr><td align="left" valign="top">• <a href="_005fgfortran_005fset_005foptions.html#g_t_005fgfortran_005fset_005foptions" accesskey="2">_gfortran_set_options</a>:</td><td> </td><td align="left" valign="top">Set library option flags
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</td></tr>
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<tr><td align="left" valign="top">• <a href="_005fgfortran_005fset_005fconvert.html#g_t_005fgfortran_005fset_005fconvert" accesskey="3">_gfortran_set_convert</a>:</td><td> </td><td align="left" valign="top">Set endian conversion
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<tr><td align="left" valign="top">• <a href="_005fgfortran_005fset_005frecord_005fmarker.html#g_t_005fgfortran_005fset_005frecord_005fmarker" accesskey="4">_gfortran_set_record_marker</a>:</td><td> </td><td align="left" valign="top">Set length of record markers
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<tr><td align="left" valign="top">• <a href="_005fgfortran_005fset_005ffpe.html#g_t_005fgfortran_005fset_005ffpe" accesskey="5">_gfortran_set_fpe</a>:</td><td> </td><td align="left" valign="top">Set when a Floating Point Exception should be raised
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<tr><td align="left" valign="top">• <a href="_005fgfortran_005fset_005fmax_005fsubrecord_005flength.html#g_t_005fgfortran_005fset_005fmax_005fsubrecord_005flength" accesskey="6">_gfortran_set_max_subrecord_length</a>:</td><td> </td><td align="left" valign="top">Set subrecord length
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</td></tr>
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</table>
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<p>Even if you are doing mixed-language programming, it is very
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likely that you do not need to know or use the information in this
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section. Since it is about the internal structure of GNU Fortran,
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it may also change in GCC minor releases.
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</p>
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<p>When you compile a <code>PROGRAM</code> with GNU Fortran, a function
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with the name <code>main</code> (in the symbol table of the object file)
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is generated, which initializes the libgfortran library and then
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calls the actual program which uses the name <code>MAIN__</code>, for
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historic reasons. If you link GNU Fortran compiled procedures
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to, e.g., a C or C++ program or to a Fortran program compiled by
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a different compiler, the libgfortran library is not initialized
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and thus a few intrinsic procedures do not work properly, e.g.
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those for obtaining the command-line arguments.
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</p>
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<p>Therefore, if your <code>PROGRAM</code> is not compiled with
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GNU Fortran and the GNU Fortran compiled procedures require
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intrinsics relying on the library initialization, you need to
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initialize the library yourself. Using the default options,
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gfortran calls <code>_gfortran_set_args</code> and
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<code>_gfortran_set_options</code>. The initialization of the former
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is needed if the called procedures access the command line
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(and for backtracing); the latter sets some flags based on the
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standard chosen or to enable backtracing. In typical programs,
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it is not necessary to call any initialization function.
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</p>
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<p>If your <code>PROGRAM</code> is compiled with GNU Fortran, you shall
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not call any of the following functions. The libgfortran
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initialization functions are shown in C syntax but using C
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bindings they are also accessible from Fortran.
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</p>
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<p>
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Next: <a href="Naming-and-argument_002dpassing-conventions.html#Naming-and-argument_002dpassing-conventions" accesskey="n" rel="next">Naming and argument-passing conventions</a>, Previous: <a href="GNU-Fortran-Compiler-Directives.html#GNU-Fortran-Compiler-Directives" accesskey="p" rel="prev">GNU Fortran Compiler Directives</a>, Up: <a href="Mixed_002dLanguage-Programming.html#Mixed_002dLanguage-Programming" accesskey="u" rel="up">Mixed-Language Programming</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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