I've been tracking down a bug where qemu run on ARM hosts will (about half of the time) abort early in execution with:
qemu-system-i386: malloc.c:3096: sYSMALLOc: Assertion `(old_top == (((mbinptr) (((char *) &((av)->bins[((1) - 1) * 2])) - __builtin_offsetof (struct malloc_chunk, fd)))) && old_size == 0) || ((unsigned long) (old_size) >= (unsigned long)((((__builtin_offsetof (struct malloc_chunk, fd_nextsize))+((2 * (sizeof(size_t))) - 1)) & ~((2 * (sizeof(size_t))) - 1))) && ((old_top)->size & 0x1) && ((unsigned long)old_end & pagemask) == 0)' failed. This turns out to be because code_gen_alloc() is using mmap(MAP_FIXED) to map the code buffer at address 0x01000000UL, which is in the area glibc happens to be using for its heap. This tends to make the next malloc() abort, although occasionally the stars align and we pass that and fail weirdly later on. I suspect we need to drop the MAP_FIXED requirement and fix the TCG code to cope with emitting code for longer-range branches for calls to host fns etc (calls/branches within the generated code should be ok to keep using the short-range branch insn I think). There is already no guarantee that the generated code and the host C code are within short branch range of each other... -- PMM
