Is there a way of configuring the emacs build to produce an executable that does not use dump/unexec functionality?
I'm trying to compile emacs with ASAN, clang and gcc's address sanitizer, enabled.
However, ASAN is an invasive compiler plugin and it's disturbing Emacs' unexec/dump functionality.
I'm using the following script to compile a "debug Emacs" from a release tarball.
#!/bin/bash
oldpwd="$(pwd)"
echo "${make_args[@]}"
tar -xvf "$oldpwd"/emacs-26.1.tar.xz
mkdir -p "$oldpwd"/out
(
cd ./emacs-26.1
./configure --prefix="$oldpwd"/out
make 'CC=gcc' 'CFLAGS=-O0 -fsanitize=address -g' 'LDFLAGS=-lpthread -lasan'
make install
)
I get the following stack trace while building emacs. The stripped-down interpreter temacs works fine, but crashes when it tries to dump its state.
==28019==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc 0x7fffef4c899e bp 0x7fffffffca90 sp 0x7fffffffca70 T0)
#0 0x7fffef4c899d in malloc_set_state (/lib64/libc.so.6+0x8599d)
#1 0x83c053 in malloc_initialize_hook ~/Downloads/emacs-26.1/src/alloc.c:164
#2 0x7fffef4c7d0e in ptmalloc_init.part.7 (/lib64/libc.so.6+0x84d0e)
#3 0x7fffef4c81dc in malloc_hook_ini (/lib64/libc.so.6+0x851dc)
#4 0x7fffef4c69ba in malloc_get_state (/lib64/libc.so.6+0x839ba)
#5 0x83c077 in alloc_unexec_pre ~/Downloads/emacs-26.1/src/alloc.c:190
#6 0x7349a0 in Fdump_emacs ~/Downloads/emacs-26.1/src/emacs.c:2218
#7 0x88c739 in eval_sub ~/Downloads/emacs-26.1/src/eval.c:2237
As far as I can tell, the offending line is in alloc.c
if (malloc_set_state (malloc_state_ptr) != 0)
emacs_abort ();
# ifndef XMALLOC_OVERRUN_CHECK
alloc_unexec_post ();
# endif
}
Where malloc_state_ptr doesn't acquire a sensible value when -fsanitize=address is enabled. I'm not sure why the normal path works, but I don't have enough familiarity with the Emacs source to figure it out.
