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authorSteve Vinoski <[email protected]>2011-02-22 18:07:57 -0500
committerSverker Eriksson <[email protected]>2011-03-24 16:45:50 +0100
commitb02f03c979cda37e43828cd6e1787649f1d8ca8c (patch)
tree6ebe11e92b89c6a78830db053a14f0f1a5edb63a /erts/doc
parentd9932cbb82954532fb39ffaa05cde74a6ec8869c (diff)
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add support for checking if an ERL_NIF_TERM is an exception
Add the enif_is_exception function to allow callers to determine whether an ERL_NIF_TERM represents an exception. (Currently the only supported exception is badarg since only enif_make_badarg exists, but this will likely be expanded in future releases.) This allows NIF code to call other NIF functions that return ERL_NIF_TERM and properly check to see if the returned terms are exceptions. Without the enif_is_exception function, developers have to create their own means of checking whether a function creates an exception, such as returning boolean success/failure indicators or some other special value indicating that an exception is in effect. The declaration of enif_is_exception in erl_nif_api_funcs.h respects the order of declarations required to keep compatibility on Windows. Add a new test to verify the operation of enif_is_exception. Modify the erl_nif man page to add a description of enif_is_exception and also to clarify the requirements of calling the enif_make_badarg function. If code calls enif_make_badarg, the env passed in gets set with exception information and so the return value of the calling function MUST be the badarg term returned from enif_make_badarg. Also clarify that the result of enif_make_badarg may be passed only to enif_is_exception and not to any other NIF API functions.
Diffstat (limited to 'erts/doc')
-rw-r--r--erts/doc/src/erl_nif.xml13
1 files changed, 12 insertions, 1 deletions
diff --git a/erts/doc/src/erl_nif.xml b/erts/doc/src/erl_nif.xml
index 4bbd4e2a54..cdce4ec0b8 100644
--- a/erts/doc/src/erl_nif.xml
+++ b/erts/doc/src/erl_nif.xml
@@ -688,6 +688,10 @@ typedef enum {
<fsummary>Determine if a term is an empty list</fsummary>
<desc><p>Return true if <c>term</c> is an empty list.</p></desc>
</func>
+ <marker id="enif_is_exception"/><func><name><ret>int</ret><nametext>enif_is_exception(ErlNifEnv* env, ERL_NIF_TERM term)</nametext></name>
+ <fsummary>Determine if a term is an exception</fsummary>
+ <desc><p>Return true if <c>term</c> is an exception.</p></desc>
+ </func>
<func><name><ret>int</ret><nametext>enif_is_fun(ErlNifEnv* env, ERL_NIF_TERM term)</nametext></name>
<fsummary>Determine if a term is a fun</fsummary>
<desc><p>Return true if <c>term</c> is a fun.</p></desc>
@@ -738,7 +742,14 @@ typedef enum {
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_badarg(ErlNifEnv* env)</nametext></name>
<fsummary>Make a badarg exception.</fsummary>
- <desc><p>Make a badarg exception to be returned from a NIF.</p></desc>
+ <desc><p>Make a badarg exception to be returned from a NIF, and set
+ an associated exception reason in <c>env</c>. If
+ <c>enif_make_badarg</c> is called, the term it returns <em>must</em>
+ be returned from the function that called it. No other return value
+ is allowed. Also, the term returned from <c>enif_make_badarg</c> may
+ be passed only to
+ <seealso marker="#enif_is_exception">enif_is_exception</seealso> and
+ not to any other NIF API function.</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_binary(ErlNifEnv* env, ErlNifBinary* bin)</nametext></name>
<fsummary>Make a binary term.</fsummary>