RFR: 8155259: Suspicious buffer allocation in com.sun.tools.javac.file.BaseFileManager

[Archie L. Cobbs]

On Thu, 20 Oct 2022 20:15:12 GMT, Archie L. Cobbs <duke at openjdk.org> wrote:

> JDK-8155259 notes that in `BaseFileManager` this code:
> 
> ByteBuffer.allocate(capacity + capacity>>1)
> 
> is actually equivalent (assuming no overflow) to:
> 
> ByteBuffer.allocate(capacity)
> 
> because in Java the `+` operator has higher precedence than the `>>` operator.
> 
> In the bug it is suggested that this be changed to reflect the presumed original intent to over-allocate by 50%, i.e.:
> 
> ByteBuffer.allocate(capacity + (capacity>>1))
> 
> however, this patch is more conservative in that it leaves the existing behavior alone and instead just simplifies it to:
> 
> ByteBuffer.allocate(capacity)
> 
> allowing us to at least resolve JDK-8155259.

I just realized this change actually fixes another bug:

> [JDK-8172106](https://bugs.openjdk.org/browse/JDK-8172106) - javac throws exception when compiling source file of size 1.5G

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PR: https://git.openjdk.org/jdk/pull/10803