RFR(M) 8252526 Remove excessive inclusion of jvmti.h and jvmtiExport.hpp

[Ioi Lam]

On 8/31/20 9:38 PM, David Holmes wrote:
> On 1/09/2020 2:00 pm, Ioi Lam wrote:
>> On 8/31/20 6:17 PM, Ioi Lam wrote:
>>> On 8/31/20 4:05 PM, David Holmes wrote:
>>>> Hi Ioi,
>>>>
>>>> I haven't looked at the code changes ...
>>>>
>>>> On 1/09/2020 4:13 am, Ioi Lam wrote:
>>>>> https://bugs.openjdk.java.net/browse/JDK-8252526
>>>>> http://cr.openjdk.java.net/~iklam/jdk16/8252526-fix-jvmti-hpp.v01/
>>>>>
>>>>> (I marked this RFR as "M" because 63 files have changed, but most 
>>>>> of the are
>>>>> just adding a missing #include "prims/jvmtiExport.hpp").
>>>>>
>>>>> jvmti.h is included 905 times and jvmtiExport.hpp is included 776 
>>>>> times
>>>>> (by 971 hotspot .o files). Most of these are unnecessarily 
>>>>> included by the
>>>>> following 3 popular header files:
>>>>>
>>>>> [1] javaClasses.hpp: ThreadStatus is rarely used, and should be moved
>>>>>      to javaThreadStatus.hpp. I also converted the enum to an C++ 11
>>>>>      enum class for better type safety. (see also JDK-8247938).
>>>>>
>>>>> [2] os.hpp: No need to include jvm.h. Use forward declaration
>>>>>      "typedef struct _jvmtiTimerInfo jvmtiTimerInfo;" instead.
>>>>
>>>> That does not seem reasonable to me. It is one thing to do a simple 
>>>> forward declaration of a class but this is an internal detail of 
>>>> JVMTI which os.hpp has no business knowing about.
>>>>
>>>
>>> How about changing jvmti.h from:
>>>
>>> struct _jvmtiTimerInfo;
>>> typedef struct _jvmtiTimerInfo jvmtiTimerInfo;
>>>
>>> to
>>>
>>> struct jvmtiTimerInfo;
>>> typedef struct jvmtiTimerInfo jvmtiTimerInfo;
>>>
>>> Then os.hpp can declare:
>>>
>>> struct jvmtiTimerInfo;
>
> Does that actually work? If so that's equivalent to "class Foo;" 
> forward declarations and so is acceptable.
Yes, it works, but I would need to file a CSR because jvmti.h is 
included in the JDK ....

Thanks
- Ioi

=======
$ hg diff
diff -r aaa4245df83a src/hotspot/share/prims/jvmtiH.xsl
--- a/src/hotspot/share/prims/jvmtiH.xsl    Mon Aug 31 11:03:13 2020 -0700
+++ b/src/hotspot/share/prims/jvmtiH.xsl    Mon Aug 31 23:24:27 2020 -0700
@@ -406,11 +406,11 @@
  </xsl:template>

  <xsl:template match="typedef" mode="early">
-  <xsl:text>struct _</xsl:text>
+  <xsl:text>struct </xsl:text>
    <xsl:value-of select="@id"/>
    <xsl:text>;
  </xsl:text>
-  <xsl:text>typedef struct _</xsl:text>
+  <xsl:text>typedef struct </xsl:text>
    <xsl:value-of select="@id"/>
    <xsl:text> </xsl:text>
    <xsl:value-of select="@id"/>
@@ -419,7 +419,7 @@
  </xsl:template>

  <xsl:template match="typedef" mode="body">
-  <xsl:text>struct _</xsl:text>
+  <xsl:text>struct </xsl:text>
    <xsl:value-of select="@id"/>
    <xsl:text> {
  </xsl:text>
diff -r aaa4245df83a src/hotspot/share/runtime/os.hpp
--- a/src/hotspot/share/runtime/os.hpp    Mon Aug 31 11:03:13 2020 -0700
+++ b/src/hotspot/share/runtime/os.hpp    Mon Aug 31 23:24:27 2020 -0700
@@ -51,7 +51,7 @@
  class OSThread;
  class Mutex;

-typedef struct _jvmtiTimerInfo jvmtiTimerInfo;
+struct jvmtiTimerInfo;

  template<class E> class GrowableArray;
=======