forked from mirrors/gecko-dev
Bug 1368932 - Allow MOZ_PASTE_PREFIX_AND_ARG_COUNT to work with 0 arguments. r=froydnj
At the same time, remove the MOZ_STATIC_ASSERT_VALID_ARG_COUNT, which doesn't actually work for more than 50 arguments(*), and which is now not useful to detect 0 arguments. (*) the build fails, but not directly thanks to the static_assert it expands to. --HG-- extra : rebase_source : 8f0fe7b352c89b5a3ec87f42ef5464c370c362ef
This commit is contained in:
Mike Hommey
parent
2357f45d41
commit
c1becb4a54
7 changed files with 27 additions and 60 deletions
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@ -314,7 +314,6 @@ MOZ_CrashPrintf(const char* aFilename, int aLine, const char* aFormat, ...);
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*/
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#define MOZ_CRASH_UNSAFE_PRINTF(format, ...) \
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do { \
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MOZ_STATIC_ASSERT_VALID_ARG_COUNT(__VA_ARGS__); \
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static_assert( \
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MOZ_PASTE_PREFIX_AND_ARG_COUNT(, __VA_ARGS__) <= sPrintfMaxArgs, \
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"Only up to 4 additional arguments are allowed!"); \
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@ -21,27 +21,29 @@
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*
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* MOZ_PASTE_PREFIX_AND_ARG_COUNT(, foo, 42) expands to 2
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* MOZ_PASTE_PREFIX_AND_ARG_COUNT(A, foo, 42, bar) expands to A3
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* MOZ_PASTE_PREFIX_AND_ARG_COUNT(A) expands to A0
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* MOZ_PASTE_PREFIX_AND_ARG_COUNT() expands to 0, but MSVC warns there
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* aren't enough arguments given.
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*
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* You must pass in between 1 and 50 (inclusive) variadic arguments, past
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* |aPrefix|. It is not legal to do
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* You must pass in between 0 and 50 (inclusive) variadic arguments, past
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* |aPrefix|.
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*
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* MOZ_PASTE_PREFIX_AND_ARG_COUNT(prefix)
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* The `##__VA_ARGS__` form is a GCC extension that removes the comma if
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* __VA_ARGS__ is empty. It is supported by Clang too. MSVC ignores ##,
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* and its default behavior is already to strip the comma when __VA_ARGS__
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* is empty.
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*
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* (that is, pass in 0 variadic arguments). To ensure that a compile-time
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* error occurs when these constraints are violated, use the
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* MOZ_STATIC_ASSERT_VALID_ARG_COUNT macro with the same variaidc arguments
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* wherever this macro is used.
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*
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* Passing (__VA_ARGS__, <rest of arguments>) rather than simply calling
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* MOZ_MACROARGS_ARG_COUNT_HELPER2(__VA_ARGS__, <rest of arguments>) very
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* carefully tiptoes around a MSVC bug where it improperly expands __VA_ARGS__
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* as a single token in argument lists. For details, see:
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*
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* http://connect.microsoft.com/VisualStudio/feedback/details/380090/variadic-macro-replacement
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* http://cplusplus.co.il/2010/07/17/variadic-macro-to-count-number-of-arguments/#comment-644
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* So MOZ_MACROARGS_ARG_COUNT_HELPER(prefix) expands to
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* (_, prefix50, prefix49, ...)
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* MOZ_MACROARGS_ARG_COUNT_HELPER(prefix, a) expands to
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* (_, a, prefix50, prefix49, ...)
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* etc.
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*/
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#define MOZ_PASTE_PREFIX_AND_ARG_COUNT(aPrefix, ...) \
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MOZ_MACROARGS_ARG_COUNT_HELPER((__VA_ARGS__, \
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MOZ_MACROARGS_ARG_COUNT_HELPER2( \
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MOZ_MACROARGS_ARG_COUNT_HELPER(aPrefix, ##__VA_ARGS__))
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#define MOZ_MACROARGS_ARG_COUNT_HELPER(aPrefix, ...) (_, ##__VA_ARGS__, \
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aPrefix##50, aPrefix##49, aPrefix##48, aPrefix##47, aPrefix##46, \
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aPrefix##45, aPrefix##44, aPrefix##43, aPrefix##42, aPrefix##41, \
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aPrefix##40, aPrefix##39, aPrefix##38, aPrefix##37, aPrefix##36, \
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@ -51,12 +53,12 @@
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aPrefix##20, aPrefix##19, aPrefix##18, aPrefix##17, aPrefix##16, \
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aPrefix##15, aPrefix##14, aPrefix##13, aPrefix##12, aPrefix##11, \
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aPrefix##10, aPrefix##9, aPrefix##8, aPrefix##7, aPrefix##6, \
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aPrefix##5, aPrefix##4, aPrefix##3, aPrefix##2, aPrefix##1, aPrefix##0))
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aPrefix##5, aPrefix##4, aPrefix##3, aPrefix##2, aPrefix##1, aPrefix##0)
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#define MOZ_MACROARGS_ARG_COUNT_HELPER(aArgs) \
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MOZ_MACROARGS_ARG_COUNT_HELPER2 aArgs
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#define MOZ_MACROARGS_ARG_COUNT_HELPER2(aArgs) \
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MOZ_MACROARGS_ARG_COUNT_HELPER3 aArgs
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#define MOZ_MACROARGS_ARG_COUNT_HELPER2( \
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#define MOZ_MACROARGS_ARG_COUNT_HELPER3(a0, \
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a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, \
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a11, a12, a13, a14, a15, a16, a17, a18, a19, a20, \
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a21, a22, a23, a24, a25, a26, a27, a28, a29, a30, \
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@ -64,33 +66,6 @@
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a41, a42, a43, a44, a45, a46, a47, a48, a49, a50, \
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a51, ...) a51
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/*
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* MOZ_STATIC_ASSERT_VALID_ARG_COUNT ensures that a compile-time error occurs
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* when the argument count constraints of MOZ_PASTE_PREFIX_AND_ARG_COUNT are
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* violated. Use this macro wherever MOZ_PASTE_PREFIX_AND_ARG_COUNT is used
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* and pass it the same variadic arguments.
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*
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* This macro employs a few dirty tricks to function. To detect the zero
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* argument case, |(__VA_ARGS__)| is stringified, sizeof-ed, and compared to
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* what it should be in the absence of arguments.
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*
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* Detecting too many arguments is a little trickier. With a valid argument
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* count and a prefix of 1, MOZ_PASTE_PREFIX_AND_ARG_COUNT expands to e.g. 14.
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* With a prefix of 0.0, it expands to e.g. 0.04. If there are too many
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* arguments, it expands to the first argument over the limit. If this
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* exceeding argument is a number, the assertion will fail as there is no
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* number than can simultaneously be both > 10 and == 0. If the exceeding
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* argument is not a number, a compile-time error should still occur due to
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* the operations performed on it.
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*/
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#define MOZ_MACROARGS_STRINGIFY_HELPER(x) #x
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#define MOZ_STATIC_ASSERT_VALID_ARG_COUNT(...) \
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static_assert( \
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sizeof(MOZ_MACROARGS_STRINGIFY_HELPER((__VA_ARGS__))) != sizeof("()") && \
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(MOZ_PASTE_PREFIX_AND_ARG_COUNT(1, __VA_ARGS__)) > 10 && \
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(int)(MOZ_PASTE_PREFIX_AND_ARG_COUNT(0.0, __VA_ARGS__)) == 0, \
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"MOZ_STATIC_ASSERT_VALID_ARG_COUNT requires 1 to 50 arguments") /* ; */
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/*
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* MOZ_ARGS_AFTER_N expands to its arguments excluding the first |N|
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* arguments. For example:
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@ -50,9 +50,7 @@
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*
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* If the |aFixedArgs| list is not empty, a trailing comma must be included.
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*
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* The |aArgs| list must be not be empty and may be up to 50 items long. Use
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* MOZ_STATIC_ASSERT_VALID_ARG_COUNT to ensure that violating this constraint
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* results in a compile-time error.
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* The |aArgs| list may be up to 50 items long.
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*/
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#define MOZ_FOR_EACH_EXPAND_HELPER(...) __VA_ARGS__
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#define MOZ_FOR_EACH_GLUE(a, b) a b
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@ -70,6 +68,7 @@
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aMacro, \
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(MOZ_FOR_EACH_EXPAND_HELPER aFixedArgs MOZ_ARG_1 aArgs))
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#define MOZ_FOR_EACH_0(m, s, fa, a)
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#define MOZ_FOR_EACH_1(m, s, fa, a) \
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MOZ_FOR_EACH_HELPER(m, fa, a)
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#define MOZ_FOR_EACH_2(m, s, fa, a) \
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@ -6,9 +6,9 @@
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#include "mozilla/MacroArgs.h"
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MOZ_STATIC_ASSERT_VALID_ARG_COUNT(1);
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MOZ_STATIC_ASSERT_VALID_ARG_COUNT(1, 2);
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static_assert(MOZ_PASTE_PREFIX_AND_ARG_COUNT(100) == 1000, "");
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static_assert(MOZ_PASTE_PREFIX_AND_ARG_COUNT(100, a) == 1001, "");
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static_assert(MOZ_PASTE_PREFIX_AND_ARG_COUNT(100, a, b) == 1002, "");
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static_assert(MOZ_PASTE_PREFIX_AND_ARG_COUNT(100, a, b, c) == 1003, "");
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static_assert(MOZ_PASTE_PREFIX_AND_ARG_COUNT(, a, b, c) == 3, "");
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@ -442,7 +442,6 @@ DowncastCCParticipant(void* aPtr)
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ImplCycleCollectionUnlink(tmp->_field);
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#define NS_IMPL_CYCLE_COLLECTION_UNLINK(...) \
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MOZ_STATIC_ASSERT_VALID_ARG_COUNT(__VA_ARGS__); \
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MOZ_FOR_EACH(NS_IMPL_CYCLE_COLLECTION_UNLINK_HELPER, (), (__VA_ARGS__))
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#define NS_IMPL_CYCLE_COLLECTION_UNLINK_END \
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@ -494,7 +493,6 @@ DowncastCCParticipant(void* aPtr)
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ImplCycleCollectionTraverse(cb, tmp->_field, #_field, 0);
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#define NS_IMPL_CYCLE_COLLECTION_TRAVERSE(...) \
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MOZ_STATIC_ASSERT_VALID_ARG_COUNT(__VA_ARGS__); \
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MOZ_FOR_EACH(NS_IMPL_CYCLE_COLLECTION_TRAVERSE_HELPER, (), (__VA_ARGS__))
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#define NS_IMPL_CYCLE_COLLECTION_TRAVERSE_RAWPTR(_field) \
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@ -156,7 +156,6 @@ NS_CI_INTERFACE_GETTER_NAME(_class)(uint32_t *count, nsIID ***array) \
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}
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#define NS_IMPL_CI_INTERFACE_GETTER(aClass, ...) \
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MOZ_STATIC_ASSERT_VALID_ARG_COUNT(__VA_ARGS__); \
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NS_CLASSINFO_HELPER_BEGIN(aClass, \
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MOZ_PASTE_PREFIX_AND_ARG_COUNT(/* No prefix */, \
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__VA_ARGS__)) \
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@ -164,7 +163,6 @@ NS_CI_INTERFACE_GETTER_NAME(_class)(uint32_t *count, nsIID ***array) \
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NS_CLASSINFO_HELPER_END
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#define NS_IMPL_QUERY_INTERFACE_CI(aClass, ...) \
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MOZ_STATIC_ASSERT_VALID_ARG_COUNT(__VA_ARGS__); \
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NS_INTERFACE_MAP_BEGIN(aClass) \
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MOZ_FOR_EACH(NS_INTERFACE_MAP_ENTRY, (), (__VA_ARGS__)) \
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NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, MOZ_ARG_1(__VA_ARGS__)) \
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@ -960,7 +960,6 @@ NS_IMETHODIMP _class::QueryInterface(REFNSIID aIID, void** aInstancePtr) \
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NS_INTERFACE_TABLE_END
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#define NS_INTERFACE_TABLE(aClass, ...) \
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MOZ_STATIC_ASSERT_VALID_ARG_COUNT(__VA_ARGS__); \
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NS_INTERFACE_TABLE_BEGIN \
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MOZ_FOR_EACH(NS_INTERFACE_TABLE_ENTRY, (aClass,), (__VA_ARGS__)) \
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NS_INTERFACE_TABLE_ENTRY_AMBIGUOUS(aClass, nsISupports, \
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@ -1041,7 +1040,6 @@ NS_IMETHODIMP_(MozExternalRefCountType) Class::Release(void) \
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#define NS_INTERFACE_TABLE_INHERITED0(Class) /* Nothing to do here */
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#define NS_INTERFACE_TABLE_INHERITED(aClass, ...) \
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MOZ_STATIC_ASSERT_VALID_ARG_COUNT(__VA_ARGS__); \
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NS_INTERFACE_TABLE_BEGIN \
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MOZ_FOR_EACH(NS_INTERFACE_TABLE_ENTRY, (aClass,), (__VA_ARGS__)) \
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NS_INTERFACE_TABLE_END
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