1115477 - Fix -Wunused and -Wtype-limits warnings in js/src

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Chris Peterson [:cpeterson]]

Attachment: fix-js-warnings.patch

Variable `id` is an object, but the printf format string specifies %d:

> js/ipc/JavaScriptLogging.h:118: warning: cannot pass objects of non-POD type 'class mozilla::jsipc::ObjectId' through '...'; call will abort at runtime

On x86 and x86-64 platforms, PostStorePrePopFP is only used in debug builds:

> js/src/asmjs/AsmJSFrameIterator.cpp:119:23 [-Wunused-const-variable] unused variable 'PostStorePrePopFP'

These `id_*` getter functions are only used in debug builds:

> js/src/jsinfer.cpp:57:1 [-Wunused-function] unused function 'id___proto__'
> js/src/jsinfer.cpp:62:1 [-Wunused-function] unused function 'id_constructor'
> js/src/jsinfer.cpp:67:1 [-Wunused-function] unused function 'id_caller'

clang complains that private member variable `padding` is never read or written. Making `padding` protected instead of private is kinda hacky, but it suppresses this -Wunused warning (because a derived class could theoretically use this protected member variable). Also convert redundant `typedef enum JSTryNoteKind` definition to `enum JSTryNoteKind`.

> js/src/jsscript.h:1876:14: error: private field 'padding' is not used [-Wunused-private-field]

The templatized `chars` parameter may be a Latin1Char or char16_t string. If `chars` is Latin1Char, then the comparison with UNIT_STATIC_LIMIT (constant 256U) is always true. To suppress this warning, copy chars into a char16_t. The StaticStrings::getUnitStringForElement() function does something similar:

https://mxr.mozilla.org/mozilla-central/source/js/src/vm/String-inl.h#372

> js/src/vm/String.cpp:778:27 [-Wtype-limits] comparison is always true due to limited range of data type
> js/src/vm/String.cpp:778:25: warning: comparison of constant 256 with expression of type 'const unsigned char' is always true [-Wtautological-constant-out-of-range-compare]

Comment 1

[Jan de Mooij [:jandem]]

Comment on attachment 8541390 [details] [diff] [review]
fix-js-warnings.patch

Review of attachment 8541390 [details] [diff] [review]:
-----------------------------------------------------------------

Great, thanks!

::: js/src/jsinfer.cpp
@@ +49,5 @@
>  using mozilla::PodZero;
>  
>  static inline jsid
>  id_prototype(JSContext *cx) {
>      return NameToId(cx->names().prototype);

Pre-existing nit: while you're here, would you mind moving the "{" to its own line? Same for the functions below. See types::TypeIdStringImpl below for what it should look like.

Comment 2

[Chris Peterson [:cpeterson]]

Thanks. Landed with fixed "{" lines:

https://hg.mozilla.org/integration/mozilla-inbound/rev/2fbdaa8a5ea7

Comment 3

[Phil Ringnalda (:philor)]

https://hg.mozilla.org/mozilla-central/rev/2fbdaa8a5ea7