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<h3 class="section">3.6 Error Reporting</h3>

<p><a name="index-error-messages-606"></a>Most of the error reporting by other functions in the library is done by
way of the functions declared in <samp><span class="file">error.h</span></samp>.  These function
communicate directly with the user through standard error.  Client
programs should also use these functions where possible for the sake of
a uniform interface.

<div class="defun">
&mdash; Function: void <b>avm_set_program_name</b> (<var>char *argv0</var>)<var><a name="index-avm_005fset_005fprogram_005fname-607"></a></var><br>
<blockquote><p>The argument to this function should be the address of a null terminated
string holding the name of the program to be reported in error messages
that begin with a program name. Typically this string will be the name
of the program as it was invoked on the command line, possibly with path
components stripped from it. An alternative would be to set it to the
name of a virtual code application being evaluated. If this function is
never called, the name <code>"avram"</code> is used by default. Space for a
copy of the program name is allocated by this function, and a fatal
memory overflow error is possible if there is insufficient space available. 
</p></blockquote></div>

<div class="defun">
&mdash; Function: char* <b>avm_program_name</b> ()<var><a name="index-avm_005fprogram_005fname-608"></a></var><br>
<blockquote><p>This function returns a pointer to a null terminated character string
holding the program name presently in use. It will be either the name
most recently set by <code>avm_set_program_name</code>, or the default name
<code>"avram"</code> if none has been set. The string whose address is
returned should not be modified by the caller. 
</p></blockquote></div>

<div class="defun">
&mdash; Function: void <b>avm_warning</b> (<var>char *message</var>)<var><a name="index-avm_005fwarning-609"></a></var><br>
<blockquote><p>This function writes the null terminated string whose address is given
to standard error, prefaced by the program name and followed by a line
break. 
</p></blockquote></div>

<div class="defun">
&mdash; Function: void <b>avm_error</b> (<var>char *message</var>)<var><a name="index-avm_005ferror-610"></a></var><br>
<blockquote><p>This function writes the null terminated string whose address is given
to standard error, prefaced by the program name and followed by a line
break, as <code>avm_warning</code>, but it then terminates the process with an
exit code of 1. 
</p></blockquote></div>

<div class="defun">
&mdash; Function: void <b>avm_fatal_io_error</b> (<var>char *message, char *filename, int reason</var>)<var><a name="index-avm_005ffatal_005fio_005ferror-611"></a></var><br>
<blockquote><p>This function is useful for reporting errors caused in the course of
reading or writing files. The message is written to standard error
prefaced by the program name, and incorporating the name of the relevant
file. The <var>reason</var> should be the error code obtained from the
standard <code>errno</code> variable, which will be translated to an
<a name="index-g_t_0040code_007bstrerror_007d-612"></a>informative message if possible by the standard <code>strerror</code> function
and appended to the message. After the message is written, the process
will terminate with an exit code of 1. 
</p></blockquote></div>

<div class="defun">
&mdash; Function: void <b>avm_non_fatal_io_error</b> (<var>char *message, char *filename, int reason</var>)<var><a name="index-avm_005fnon_005ffatal_005fio_005ferror-613"></a></var><br>
<blockquote><p>This function does the same as <code>avm_fatal_io_error</code> except that it
doesn't exit the program, and allows control to return to the caller,
which should take appropriate action. 
</p></blockquote></div>

<div class="defun">
&mdash; Function: void <b>avm_internal_error</b> (<var>int code</var>)<var><a name="index-avm_005finternal_005ferror-614"></a></var><br>
<blockquote><p>This function is used to report internal errors and halt the
program. The error message is written to standard error prefaced by the
program name and followed by a line break. The code should be a unique
integer constant (i.e., not one that's used for any other internal
error), that will be printed as part of the error message as an aid to
the maintainer.

        <p>This function should be used by client programs only in the event of
conditions that constitute some violation of a required invariant. It
indicates to the user that something has gone wrong with the program,
for which a bug report would be appropriate. 
</p></blockquote></div>

<div class="defun">
&mdash; Function: void <b>avm_reclamation_failure</b> (<var>char *entity, counter count</var>)<var><a name="index-avm_005freclamation_005ffailure-615"></a></var><br>
<blockquote><p>This function is used only by the <code>avm_count</code> functions to report
unreclaimed storage. The <var>count</var> is the number of units of
storage left unreclaimed, and the <var>entity</var> is the address of
a null terminated string describing the type of unreclaimed entity, such
as <code>"lists"</code> or <code>"branches"</code>. The message is written to
standard error followed by a line break, but the program is not halted
and control returns to the caller. 
</p></blockquote></div>

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