[ruby-core:102735] [Ruby master Bug#16784] Compiling with --enable-load-relative and "musl-gcc -static" yields "negative string size (or size too big) (ArgumentError)"

Issue #16784 has been updated by xtkoba (Tee KOBAYASHI).


I have confirmed this issue with a recent 3.1.0dev version (33dc0a070a):
```
$ ./miniruby -e ""
./miniruby: negative string size (or size too big) (ArgumentError)
```

An observation using GDB:
```
Breakpoint 1, ruby_init_loadpath () at ../ruby.c:614
614         VALUE load_path, archlibdir = 0;
(gdb) next
616         const char *paths = ruby_initial_load_paths;
(gdb)
630         sopath = runtime_libruby_path();
(gdb)
631         libpath = RSTRING_PTR(sopath);
(gdb)
633         p = strrchr(libpath, '/');
(gdb)
634         if (p) {
(gdb)
675         baselen = p - libpath;
(gdb)
676         rb_str_resize(sopath, baselen);
(gdb) p baselen
$1 = 18446743798821772880
(gdb) p p
$2 = 0x0
(gdb) p libpath
$3 = 0x400096a1b0 ""
```

It seems that in line 675 `baselen` is set to a wrong value when `p` is equal to `NULL`.

A proposed workaround:
```
--- a/ruby.c
+++ b/ruby.c
@@ -671,8 +671,11 @@
 	    p = p2;
 	}
 #endif
+	baselen = p - libpath;
+    }
+    else {
+	baselen = 0;
     }
-    baselen = p - libpath;
     rb_str_resize(sopath, baselen);
     libpath = RSTRING_PTR(sopath);
 #define PREFIX_PATH() sopath
```

----------------------------------------
Bug #16784: Compiling with --enable-load-relative and "musl-gcc -static" yields "negative string size (or size too big) (ArgumentError)" 
https://bugs.ruby-lang.org/issues/16784#change-90741

* Author: runlevel5 (Trung Le)
* Status: Open
* Priority: Normal
* ruby -v: ruby 2.6.6p146 (2020-03-31 revision 67876) [powerpc64le-linux-musl]
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN
----------------------------------------
```
$ uname -ar
Linux localhost 5.4.27-0-lts #1-Alpine SMP Mon, 23 Mar 2020 18:15:20 UTC ppc64le Linux

$ gcc --version
gcc (Alpine 9.2.0) 9.2.0
Copyright (C) 2019 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ apk info musl
musl-1.1.24-r2 description:
the musl c library (libc) implementation

ruby-2.6.6> CC="gcc -static" ./configure --enable-load-relative

Configuration summary for ruby version 2.6.6

   * Installation prefix: /usr/local
   * exec prefix:         ${prefix}
   * arch:                powerpc64le-linux-musl
   * site arch:           ${arch}
   * RUBY_BASE_NAME:      ruby
   * ruby lib prefix:     ${libdir}/${RUBY_BASE_NAME}
   * site libraries path: ${rubylibprefix}/${sitearch}
   * vendor path:         ${rubylibprefix}/vendor_ruby
   * target OS:           linux-musl
   * compiler:            gcc -static
   * with pthread:        yes
   * enable shared libs:  no
   * dynamic library ext: so
   * CFLAGS:              ${optflags} ${debugflags} ${warnflags}
   * LDFLAGS:             -L. -fstack-protector-strong -rdynamic \
                          -Wl,-export-dynamic
   * DLDFLAGS:            -Wl,--compress-debug-sections=zlib
   * optflags:            -O3
   * debugflags:          -ggdb3
   * warnflags:           -Wall -Wextra -Wdeclaration-after-statement \
                          -Wdeprecated-declarations -Wduplicated-cond \
                          -Wimplicit-function-declaration -Wimplicit-int \
                          -Wmisleading-indentation -Wpointer-arith \
                          -Wrestrict -Wwrite-strings \
                          -Wimplicit-fallthrough=0 -Wmissing-noreturn \
                          -Wno-cast-function-type \
                          -Wno-constant-logical-operand -Wno-long-long \
                          -Wno-missing-field-initializers \
                          -Wno-overlength-strings \
                          -Wno-packed-bitfield-compat \
                          -Wno-parentheses-equality -Wno-self-assign \
                          -Wno-tautological-compare -Wno-unused-parameter \
                          -Wno-unused-value -Wsuggest-attribute=format \
                          -Wsuggest-attribute=noreturn -Wunused-variable
   * strip command:       strip -S -x
   * install doc:         yes
   * JIT support:         yes
   * man page type:       man


ruby-2.6.6> make
...
building rb_mjit_header.h
linking miniruby
rb_mjit_header.h updated
generating encdb.h
building .ext/include/powerpc64le-linux-musl/rb_mjit_min_header-2.6.6.h
./miniruby -I./lib -I. -I.ext/common  ./tool/transform_mjit_header.rb "gcc -static " rb_mjit_header.h .ext/include/powerpc64le-linux-musl/rb_mjit_min_header-2.6.6.h
Traceback (most recent call last):
Traceback (most recent call last):
./miniruby: negative string size (or size too big) (ArgumentError)
./miniruby: negative string size (or size too big) (ArgumentError)
make: *** [uncommon.mk:781: .rbconfig.time] Error 1
make: *** Waiting for unfinished jobs....
make: *** [uncommon.mk:233: .ext/include/powerpc64le-linux-musl/rb_mjit_min_header-2.6.6.h] Error 1
Traceback (most recent call last):
./miniruby: negative string size (or size too big) (ArgumentError)
make: *** [uncommon.mk:1033: encdb.h] Error 1

ruby-2.6.6> ./miniruby
./miniruby: negative string size (or size too big) (ArgumentError)
```

Seems to me the miniruby binary is not correctly compiled if CC is `musl-gcc -static` (static linking) and `--enable-load-relative` option is enabled.






-- 
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