Request for review: support building hotspot with gcc 4.6

[David Holmes]

Dave,

David Katleman said the following on 04/30/11 09:13:
> Hi Omair!
> 
> On 4/29/2011 3:59 PM, Omair Majid wrote:
>> Hi,
>>
>> http://cr.openjdk.java.net/~omajid/webrevs/gcc-46-support/
>>
>> The patch adds support for building hotspot with gcc 4.6. gcc 4.6 
>> changed how arguments are handled. It now treats -export-dynamic as it 
>> treats any other -efoo option: it thinks xport-dynamic is the entry 
>> point and passes this information to the linker. Since -export-dynamic 
>> is not passed to the linker, not all symbols will be exported by the 
>> linker. The bfd-based linker, given the invalid entry point 
>> xport-dynamic, simply ignores it. The gold linker, however, crashes 
>> causing the build to fail.
>>
>> Since -export-dynamic is a linker option, the correct way to pass it 
>> is using -Wl,-export-dynamic (or -Xlinker -export-dynamic). We have 
>> had this patch in IcedTea6 for a while now, but it would be nice if 
>> this was in OpenJDK too.
> 
> Seems like your change should be surrounded by an ifneq that enables 
> your change for 4.6 and later

Changing the use of a linker option:

  -foo

to

-Xlinker -foo  (or -Wl,-foo)

is fully compatible and preferable. We've been making a number of such 
changes ourselves (-Xlinker form) because they are needed when working 
with some of the cross-compilers we use for embedded.

David Holmes
------------

> Example elsewhere in the file
> 
>>   129 # Except for a few acceptable ones
>>   130 # Since GCC 4.3, -Wconversion has changed its meanings to warn 
>> these implicit
>>   131 # conversions which might affect the values. To avoid that, we 
>> need to turn
>>   132 # it off explicitly.
>>   133 ifneq "$(shell expr \( $(CC_VER_MAJOR) \>  4 \) \| \( \( 
>> $(CC_VER_MAJOR) = 4 \) \&  \( $(CC_VER_MINOR) \>= 3 \) \))" "0"
>>   134 ACCEPTABLE_WARNINGS = -Wpointer-arith -Wsign-compare
>>   135 else
>>   136 ACCEPTABLE_WARNINGS = -Wpointer-arith -Wconversion -Wsign-compare
>>   137 endif
> 
> Thanks
>         Dave
>