RFR: 8342860: Fix more NULL usage backsliding [v2]

[theoweidmannoracle]

On Tue, 5 Nov 2024 16:02:07 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

> Can you use the (updated) regex in the JBS issue description to verify the only remaining "NULL"s in src/hotspot are the jvmti.{xml,xls} files and the globalDefinitions_{gcc,visCPP}.hpp files?
> 
> There are also some NULLs recently introduced in test/hotspot: ./jtreg/serviceability/jvmti/GetMethodDeclaringClass/libTestUnloadedClass.cpp ./jtreg/serviceability/jvmti/vthread/VThreadEventTest/libVThreadEventTest.cpp
> 
> (Found by applying the same regex to test/hotspot, and then removing .java and .c files.)
> 
> There are a few other files in test/hotspot containing NULLs: ./jtreg/vmTestbase/nsk/share/jni/README ./jtreg/vmTestbase/nsk/share/jvmti/README These are documentation files with examples written in C, so should not be changed.
> 
> ./jtreg/vmTestbase/nsk/share/native/nsk_tools.hpp In a comment describing a string to be used for printing. Uses would need to be examined to ensure it's okay to change the string used for a null value. I think I planned to do this as a followup to JDK-8324799, and then forgot. I'd be okay with doing something about this being separate from the current PR. While the necessary textual changes are probably small, there's a lot of uses to examine to be sure a change is okay.

@kimbarrett I fixed the backslides in the *.cpp files you mentioned. The egrep outputs are now:


% find test/hotspot -type f ! -name "*.c" ! -name "*.java" -exec egrep -H "[^[:alnum:]_]NULL([^[:alnum:]_]|$)" {} ;
test/hotspot/jtreg/vmTestbase/nsk/share/native/nsk_tools.hpp: * Returns str or "<NULL>" if str is null; useful for printing strings.
test/hotspot/jtreg/vmTestbase/nsk/share/jvmti/README:    if (!NSK_JVMTI_VERIFY(jvmti->GetVersion(&version) != NULL)) {
test/hotspot/jtreg/vmTestbase/nsk/share/jni/README:            jni->FindClass(class_name) != NULL)) {
test/hotspot/jtreg/vmTestbase/nsk/share/jni/README:            jni->FindClass(class_name)) != NULL)) {


and 


egrep -R "[^[:alnum:]_]NULL([^[:alnum:]_]|$)" src/hotspot                                                      
src/hotspot/share/prims/jvmti.xml:    or return value. A "null pointer" is C <code>NULL</code> or C++ <code>nullptr</code>.
src/hotspot/share/prims/jvmti.xml:                       &methodName, NULL, NULL);
src/hotspot/share/prims/jvmti.xml:  GetThreadCpuTime(env, NULL, nanos_ptr)
src/hotspot/share/prims/jvmti.xsl:        <xsl:value-of select="@const"/>, NULL)</code>
src/hotspot/share/utilities/globalDefinitions_visCPP.hpp:// When __cplusplus is defined, NULL is defined as 0 (32-bit constant) in
src/hotspot/share/utilities/globalDefinitions_visCPP.hpp:// On 64-bit architectures, defining NULL as a 32-bit constant can cause
src/hotspot/share/utilities/globalDefinitions_visCPP.hpp:// varargs, we pass the argument 0 as an int.  So, if NULL was passed to a
src/hotspot/share/utilities/globalDefinitions_visCPP.hpp:// only 32-bits of the "NULL" pointer may be initialized to zero.  The
src/hotspot/share/utilities/globalDefinitions_visCPP.hpp:// Solution: For 64-bit architectures, redefine NULL as 64-bit constant 0.
src/hotspot/share/utilities/globalDefinitions_visCPP.hpp:#undef NULL
src/hotspot/share/utilities/globalDefinitions_visCPP.hpp:#define NULL 0LL
src/hotspot/share/utilities/globalDefinitions_visCPP.hpp:#ifndef NULL
src/hotspot/share/utilities/globalDefinitions_visCPP.hpp:#define NULL 0
src/hotspot/share/utilities/globalDefinitions_visCPP.hpp:// NULL vs NULL_WORD:
src/hotspot/share/utilities/globalDefinitions_visCPP.hpp:// On Linux NULL is defined as a special type '__null'. Assigning __null to
src/hotspot/share/utilities/globalDefinitions_visCPP.hpp:#define NULL_WORD NULL
src/hotspot/share/utilities/globalDefinitions_gcc.hpp:// NULL vs NULL_WORD:
src/hotspot/share/utilities/globalDefinitions_gcc.hpp:// On Linux NULL is defined as a special type '__null'. Assigning __null to
src/hotspot/share/utilities/globalDefinitions_gcc.hpp:  #define NULL_WORD  NULL

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PR Comment: https://git.openjdk.org/jdk/pull/21826#issuecomment-2461610347