On Wed, 4 Dec 2024 16:04:01 GMT, SendaoYan <s...@openjdk.org> wrote:
>> Hi all,
>> The file src/java.base/share/native/libjli/java.c generate false positive
>> compile warning by gcc14 with gcc options `-fsanitize=undefined -O2`, and
>> make jdk build error when configure with option `--enable-asan
>> --enable-ubsan`. So I think it's necessory to disable the false positive
>> compile warning to make jdk build normally with configure option
>> `--enable-asan --enable-ubsan`.
>>
>> This PR use gcc `_Pragma` to disbale the `-Wformat-truncation` compile
>> warning, to make the disable code area as small as possible, and make the
>> change looks ugly. There is another solution to disable the compile warning
>> seen as below, but it will disable the compile warning of java.c. So I use
>> the first solution.
>>
>>
>>
>> diff --git a/make/modules/java.base/lib/CoreLibraries.gmk
>> b/make/modules/java.base/lib/CoreLibraries.gmk
>> index 61ac495968a..5bc83cf0978 100644
>> --- a/make/modules/java.base/lib/CoreLibraries.gmk
>> +++ b/make/modules/java.base/lib/CoreLibraries.gmk
>> @@ -178,6 +178,7 @@ $(eval $(call SetupJdkLibrary, BUILD_LIBJLI, \
>> OPTIMIZATION := HIGH, \
>> CFLAGS := $(LIBJLI_CFLAGS) $(LIBZ_CFLAGS), \
>> DISABLED_WARNINGS_gcc := unused-function unused-variable, \
>> + DISABLED_WARNINGS_gcc_java.c := format-truncation, \
>> DISABLED_WARNINGS_clang := deprecated-non-prototype format-nonliteral \
>> unused-function, \
>> DISABLED_WARNINGS_clang_java_md_macosx.m := unused-variable, \
>
> SendaoYan has updated the pull request incrementally with one additional
> commit since the last revision:
>
> Fix compile warning C4068: unknown pragma 'GCC' on windows
The part that I don't understand is why the `s` is being considered as having a
`NULL` value for the gcc compiler to generate that warning for the `snprintf`
call:
if (s == NULL)
return;
s = JLI_WildcardExpandClasspath(s);
if (sizeof(format) - 2 + JLI_StrLen(s) < JLI_StrLen(s))
// s is became corrupted after expanding wildcards
return;
size_t defSize = sizeof(format)
- 2 /* strlen("%s") */
+ JLI_StrLen(s);
def = JLI_MemAlloc(defSize);
snprintf(def, defSize, format, s);
```
It looks like the compiler is considering `s = JLI_WildcardExpandClasspath(s);`
to be returning `NULL` (if I comment that line out) the warning is gone. The
other part to this is, I can't get the warning to be generated with gcc 13.x.
So I don't know if this is a bug in gcc 14.x or some kind of improvement in
detecting some genuine issue.
-------------
PR Comment: https://git.openjdk.org/jdk/pull/22546#issuecomment-2545418968
