why afl-clang-lto have built but can't configure

[Squirre17]

error message as following: (export LLVM_CONFIG="llvm-config-12")

# squ @ squ-Precision-5510 in ~/fuzz101/3/tcpdump-tcpdump-4.9.2 [22:15:56] 
$ AFL_USE_ASAN=1 CC=afl-clang-lto ./configure --prefix="$INS"
checking build system type... x86_64-unknown-linux-gnu
checking host system type... x86_64-unknown-linux-gnu
checking for gcc... afl-clang-lto
checking whether the C compiler works... no
configure: error: in `/home/squ/fuzz101/3/tcpdump-tcpdump-4.9.2':
configure: error: C compiler cannot create executables
See `config.log' for more details

afl-clang-lto have compiled already

# squ @ squ-Precision-5510 in ~/tools/AFLplusplus on git:stable x [22:22:05] 
$ afl-clang-lto                                                                                  
afl-cc++4.05a by Michal Zalewski, Laszlo Szekeres, Marc Heuse

afl-cc/afl-c++ [options]

This is a helper application for afl-fuzz. It serves as a drop-in replacement
for gcc and clang, letting you recompile third-party code with the required
runtime instrumentation. A common use pattern would be one of the following:

  CC=afl-cc CXX=afl-c++ ./configure --disable-shared
  cmake -DCMAKE_C_COMPILERC=afl-cc -DCMAKE_CXX_COMPILER=afl-c++ .
  CC=afl-cc CXX=afl-c++ meson

                                       |------------- FEATURES -------------|
MODES:                                  NCC PERSIST DICT   LAF CMPLOG SELECT
  [LTO] llvm LTO:          AVAILABLE [SELECTED]
      PCGUARD              DEFAULT      yes yes     yes    yes yes    yes
      CLASSIC                           yes yes     yes    yes yes    yes
  [LLVM] llvm:             AVAILABLE
      PCGUARD              DEFAULT      yes yes     module yes yes    yes
      CLASSIC                           no  yes     module yes yes    yes
        - NORMAL
        - CALLER
        - CTX
        - NGRAM-{2-16}
  [GCC_PLUGIN] gcc plugin: AVAILABLE
      CLASSIC              DEFAULT      no  yes     no     no  no     yes
  [GCC/CLANG] simple gcc/clang: AVAILABLE
      CLASSIC              DEFAULT      no  no      no     no  no     no

Modes:
  To select the compiler mode use a symlink version (e.g. afl-clang-fast), set
  the environment variable AFL_CC_COMPILER to a mode (e.g. LLVM) or use the
  command line parameter --afl-MODE (e.g. --afl-llvm). If none is selected,
  afl-cc will select the best available (LLVM -> GCC_PLUGIN -> GCC).
  The best is LTO but it often needs RANLIB and AR settings outside of afl-cc.

Sub-Modes: (set via env AFL_LLVM_INSTRUMENT, afl-cc selects the best available)
  PCGUARD: Dominator tree instrumentation (best!) (README.llvm.md)
  LLVM-NATIVE:  use llvm's native PCGUARD instrumentation (less performant)
  CLASSIC: decision target instrumentation (README.llvm.md)
  CALLER:  CLASSIC + single callee context (instrumentation/README.ctx.md)
  CTX:     CLASSIC + full callee context (instrumentation/README.ctx.md)
  NGRAM-x: CLASSIC + previous path ((instrumentation/README.ngram.md)

Features: (see documentation links)
  NCC:    non-colliding coverage [automatic] (that is an amazing thing!)
          (instrumentation/README.lto.md)
  PERSIST: persistent mode support [code] (huge speed increase!)
          (instrumentation/README.persistent_mode.md)
  DICT:   dictionary in the target [yes=automatic or llvm module pass]
          (instrumentation/README.lto.md + instrumentation/README.llvm.md)
  LAF:    comparison splitting [env] (instrumentation/README.laf-intel.md)
  CMPLOG: input2state exploration [env] (instrumentation/README.cmplog.md)
  SELECT: selective instrumentation (allow/deny) on filename or function [env]
          (instrumentation/README.instrument_list.md)

To see all environment variables for the configuration of afl-cc use "-hh".

For any information on the available instrumentations and options please 
consult the README.md, especially section 3.1 about instrumenting targets.

afl-cc LTO with ld= -flto=full
afl-cc LLVM version 12 using the binary path "/usr/lib/llvm-12/bin".
Compiled with shmat support.

Do not be overwhelmed :) afl-cc uses good defaults if no options are selected.
Read the documentation for FEATURES though, all are good but few are defaults.
Recommended is afl-clang-lto with AFL_LLVM_CMPLOG or afl-clang-fast with
AFL_LLVM_CMPLOG and AFL_LLVM_DICT2FILE.

have anyone can give me little tips to figure out this question.

[vanhauser-thc]

what happens if you do afl-clang-lto -o test-instr test-instr.c in the afl++ source directory?

[vanhauser-thc]

also what happens if you do CC=clang-12 CFLAGS="-fsanitize=address" ./configure --prefix="$INS"?

[Squirre17]

afl-clang-lto -o test-instr test-instr.c print a error message : "clang error: no such file or directory :'/usr/local/bin/../lib/afl/afl-llvm-rt-lto.o'"

[Squirre17]

CC=clang-12 CFLAGS="-fsanitize=address" ./configure --prefix="$INS" print out a configure error (seems like the problem associated with tcpdump itself), but cuz my Ubuntu backup laptop crashed out few days ago, I can't ssh or into Desktop and copy the message. I need time to fix it. I will add the error message after a while.

[vanhauser-thc]

in the afl++ directory please execute make clean; make all; sudo make install then retry with the afl-clang-lto command from above. your installation is broken.