bug#81211: #81211 31.0.90; Android build fails with current Java compilers

Johan Myréen <[email protected]> writes:

> In the emacs/exec directory the linker is passed an obscure option
> -Ttext=0x2000000000, which I presume is trying to say that the text
> segment should be placed starting at address 0x200000000 (?):
>
> /opt/android-ndk/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android21-clang -c -O -g loader-aarch64.s -o loader-aarch64.o
> clang: warning: argument unused during compilation: '-O' [-Wunused-command-line-argume
> nt]
> /opt/android-ndk/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android21-clang -o loader -nostdlib -nostartfiles -static -
> Wl,-Ttext=0x2000000000 loader-aarch64.o
>
> I don't know for which compiler/linker combination the Makefile is
> generated for, since, as far as I can tell, both lld and GNU ld use
> the -T switch to specify a linker script file.

-Ttext is distinct from -T.  -Ttext=0xN is equivalent to specifying the
address provided as the `--section-start' for the text segment, the
effect of which should only be to set the base address of the section
metadata.

> Anyway, the outcome of the linker invocation above results in a huge
> binary file consisting mostly of null bytes. The size of the file is
> 137436859800 bytes, which happens to be a little less than
> 0x200000000. Likewise the file libloader.so, which is included in the
> Android Emacs installer file is 137 GB in size; examining an older
> emacs.apk file reveals that the correct size is about 7.3 kB.
>
> I'm hoping for someone who knows more about the Android Emacs build
> process to step forward and clarify what went wrong, and how to
> correct it.

Which version of the NDK is this?  I cannot reproduce this problem with
NDK r28, which (for aarch64) generates such a loader executable:

ELF Header:
  Magic:   7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00 
  Class:                             ELF64
  Data:                              2's complement, little endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              EXEC (Executable file)
  Machine:                           AArch64
  Version:                           0x1
  Entry point address:               0x2000000000
  Start of program headers:          64 (bytes into file)
  Start of section headers:          19232 (bytes into file)
  Flags:                             0x0
  Size of this header:               64 (bytes)
  Size of program headers:           56 (bytes)
  Number of program headers:         4
  Size of section headers:           64 (bytes)
  Number of section headers:         11
  Section header string table index: 9