RFR: 8346719: Add relaunchers to the static JDK image for missing executables [v6]

[Jiangli Zhou]

On Tue, 9 Sep 2025 13:15:57 GMT, Magnus Ihse Bursie <ihse at openjdk.org> wrote:

>> In the static JDK image, a single humongous java executable is generated, and no other launcher, such as javac. This makes it impossible to run our jtreg tests, which assume these are present.
>> 
>> The solution is fortunately simply: we just need to add a bunch of trivial launchers, which are thin wrappers that execute the main java binary, with the proper arguments. This will result in the same behavior as the normal dynamic launchers, only that we will need to take the detour of launching another process instead of calling directly into the JLI library.
>
> Magnus Ihse Bursie has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update based on review

src/java.base/share/native/launcher/main.c line 41:

> 39: 
> 40: // This is reported when requesting a full version
> 41: static char* launcher = LAUNCHER_NAME;

Is it guaranteed that `LAUNCHER_NAME` is always defined at build time? Is it safer to keep the `ifdef LAUNCHER_NAME` check and initialize `launcer` to `NULL` if `LAUNCHER_NAME` is not defined? From removed defines.h:


#ifdef LAUNCHER_NAME
static const char* const_launcher = LAUNCHER_NAME;
#else  /* LAUNCHER_NAME */
static char* const_launcher = NULL;
#endif /* LAUNCHER_NAME */

src/java.base/share/native/launcher/main.c line 44:

> 42: 
> 43: // This is used as the name of the executable in the help message
> 44: static char* progname = PROGNAME;

Same question for `PROGNAME` as the one for `LAUNCHER_NAME` above.

src/java.base/share/native/launcher/main.c line 61:

> 59:         cpwildcard = JNI_FALSE;
> 60:     }
> 61:     if (strncmp(arg, "-J-DjavaLauncherProgname=", 26) == 0) {

It's better to replace the hardcoded string length with `strlen()` or `JLI_StrLen()`, e.g.:


const char *progname_prefix = "-J-DjavaLauncherProgname=";
int progname_prefix_len = strlen(progname_prefix);
if (strncmp(arg, "-J-DjavaLauncherProgname=", progname_prefix_len) == 0) {
    progname = arg + progname_prefix_len;
...

src/java.base/windows/native/launcher/relauncher.c line 1:

> 1: /*

How did you test the relauncher for Windows? Can you remind me if static JDK is support for Windows?

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PR Review Comment: https://git.openjdk.org/jdk/pull/24380#discussion_r2338153342
PR Review Comment: https://git.openjdk.org/jdk/pull/24380#discussion_r2338163122
PR Review Comment: https://git.openjdk.org/jdk/pull/24380#discussion_r2338170678
PR Review Comment: https://git.openjdk.org/jdk/pull/24380#discussion_r2338210218