[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH 0/2] hvmloader: drop usage of system headers
On 24/02/2021 10:26, Roger Pau Monne wrote: > Hello, > > Following two patches aim to make hvmloader standalone, so that it don't > try to use system headers. It shouldn't result in any functional > change. > > Thanks, Roger. After some experimentation in the arch container Given foo.c as: #include <stdint.h> extern uint64_t bar; uint64_t foo(void) { return bar; } int main(void) { return 0; } The preprocessed form with `gcc -m32 -E` is: # 1 "foo.c" # 1 "<built-in>" # 1 "<command-line>" # 31 "<command-line>" # 1 "/usr/include/stdc-predef.h" 1 3 4 # 32 "<command-line>" 2 # 1 "foo.c" # 1 "/usr/lib/gcc/x86_64-pc-linux-gnu/8.3.0/include/stdint.h" 1 3 4 # 9 "/usr/lib/gcc/x86_64-pc-linux-gnu/8.3.0/include/stdint.h" 3 4 # 1 "/usr/include/stdint.h" 1 3 4 # 26 "/usr/include/stdint.h" 3 4 # 1 "/usr/include/bits/libc-header-start.h" 1 3 4 # 33 "/usr/include/bits/libc-header-start.h" 3 4 # 1 "/usr/include/features.h" 1 3 4 # 450 "/usr/include/features.h" 3 4 # 1 "/usr/include/sys/cdefs.h" 1 3 4 # 452 "/usr/include/sys/cdefs.h" 3 4 # 1 "/usr/include/bits/wordsize.h" 1 3 4 # 453 "/usr/include/sys/cdefs.h" 2 3 4 # 1 "/usr/include/bits/long-double.h" 1 3 4 # 454 "/usr/include/sys/cdefs.h" 2 3 4 # 451 "/usr/include/features.h" 2 3 4 # 474 "/usr/include/features.h" 3 4 # 1 "/usr/include/gnu/stubs.h" 1 3 4 # 1 "/usr/include/gnu/stubs-32.h" 1 3 4 # 8 "/usr/include/gnu/stubs.h" 2 3 4 # 475 "/usr/include/features.h" 2 3 4 # 34 "/usr/include/bits/libc-header-start.h" 2 3 4 # 27 "/usr/include/stdint.h" 2 3 4 # 1 "/usr/include/bits/types.h" 1 3 4 # 27 "/usr/include/bits/types.h" 3 4 # 1 "/usr/include/bits/wordsize.h" 1 3 4 # 28 "/usr/include/bits/types.h" 2 3 4 # 1 "/usr/include/bits/timesize.h" 1 3 4 # 29 "/usr/include/bits/types.h" 2 3 4 # 31 "/usr/include/bits/types.h" 3 4 typedef unsigned char __u_char; ... while the freestanding form with `gcc -ffreestanding -m32 -E` is: # 1 "foo.c" # 1 "<built-in>" # 1 "<command-line>" # 1 "foo.c" # 1 "/usr/lib/gcc/x86_64-pc-linux-gnu/8.3.0/include/stdint.h" 1 3 4 # 11 "/usr/lib/gcc/x86_64-pc-linux-gnu/8.3.0/include/stdint.h" 3 4 # 1 "/usr/lib/gcc/x86_64-pc-linux-gnu/8.3.0/include/stdint-gcc.h" 1 3 4 # 34 "/usr/lib/gcc/x86_64-pc-linux-gnu/8.3.0/include/stdint-gcc.h" 3 4 # 34 "/usr/lib/gcc/x86_64-pc-linux-gnu/8.3.0/include/stdint-gcc.h" 3 4 typedef signed char int8_t; ... I can compile and link trivial programs using -m32 and stdint.h without any issue. Clearly something more subtle is going on with our choice of options when compiling hvmloader, but it certainly looks like stdint.h is fine to use in the way we want to use it. ~Andrew
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