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lcn2 / calc

C-style arbitrary precision calculator
http://www.isthe.com/chongo/tech/comp/calc/index.html
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Fix memory leak in zrandom.c #142

Closed ashamedbit closed 8 months ago

ashamedbit commented 8 months ago

Hello, I am a new contributor to the repository.

I tried to fix following issue: #47 Memory leak on make clobber all chk. I was able to reproduce the following leaks which are slightly different from the ones above:

=================================================================
==965935==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 40 byte(s) in 1 object(s) allocated from:
    #0 0x7fc0559f1808 in __interceptor_malloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cc:144
    #1 0x7fc05520ee6e in alloc /home/aniruddhan/Downloads/calc/zmath.c:242
    #2 0x7fc055217b76 in zdiv /home/aniruddhan/Downloads/calc/zmath.c:1008
    #3 0x7fc05521870f in zmod /home/aniruddhan/Downloads/calc/zmath.c:1069
    #4 0x7fc055225a2c in zsquaremod /home/aniruddhan/Downloads/calc/zmod.c:122
    #5 0x7fc055271be0 in zsrandom1 /home/aniruddhan/Downloads/calc/zrandom.c:2337
    #6 0x7fc054fececf in f_srandom /home/aniruddhan/Downloads/calc/func.c:1320
    #7 0x7fc055080f32 in builtinfunc /home/aniruddhan/Downloads/calc/func.c:13433
    #8 0x7fc0550eb6dd in o_call /home/aniruddhan/Downloads/calc/opcodes.c:2725
    #9 0x7fc0550f5b10 in calculate /home/aniruddhan/Downloads/calc/opcodes.c:4179
    #10 0x7fc0550eb628 in o_usercall /home/aniruddhan/Downloads/calc/opcodes.c:2716
    #11 0x7fc0550f5b10 in calculate /home/aniruddhan/Downloads/calc/opcodes.c:4179
    #12 0x7fc054f738aa in evaluate /home/aniruddhan/Downloads/calc/codegen.c:300
    #13 0x7fc054f7349d in getcommands /home/aniruddhan/Downloads/calc/codegen.c:230
    #14 0x7fc054f7336e in getcommands /home/aniruddhan/Downloads/calc/codegen.c:187
    #15 0x559b1cca636e in main /home/aniruddhan/Downloads/calc/calc.c:669
    #16 0x7fc053eab082 in __libc_start_main ../csu/libc-start.c:308

Direct leak of 40 byte(s) in 1 object(s) allocated from:
    #0 0x7fc0559f1808 in __interceptor_malloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cc:144
    #1 0x7fc05520ee6e in alloc /home/aniruddhan/Downloads/calc/zmath.c:242
    #2 0x7fc055217b76 in zdiv /home/aniruddhan/Downloads/calc/zmath.c:1008
    #3 0x7fc05521870f in zmod /home/aniruddhan/Downloads/calc/zmath.c:1069
    #4 0x7fc055225a2c in zsquaremod /home/aniruddhan/Downloads/calc/zmod.c:122
    #5 0x7fc0552750ff in zrandom /home/aniruddhan/Downloads/calc/zrandom.c:2951
    #6 0x7fc054feb1ae in f_random /home/aniruddhan/Downloads/calc/func.c:1207
    #7 0x7fc055081556 in builtinfunc /home/aniruddhan/Downloads/calc/func.c:13452
    #8 0x7fc0550eb6dd in o_call /home/aniruddhan/Downloads/calc/opcodes.c:2725
    #9 0x7fc0550f5b10 in calculate /home/aniruddhan/Downloads/calc/opcodes.c:4179
    #10 0x7fc0550eb628 in o_usercall /home/aniruddhan/Downloads/calc/opcodes.c:2716
    #11 0x7fc0550f5b10 in calculate /home/aniruddhan/Downloads/calc/opcodes.c:4179
    #12 0x7fc054f738aa in evaluate /home/aniruddhan/Downloads/calc/codegen.c:300
    #13 0x7fc054f7349d in getcommands /home/aniruddhan/Downloads/calc/codegen.c:230
    #14 0x7fc054f7336e in getcommands /home/aniruddhan/Downloads/calc/codegen.c:187
    #15 0x559b1cca636e in main /home/aniruddhan/Downloads/calc/calc.c:669
    #16 0x7fc053eab082 in __libc_start_main ../csu/libc-start.c:308

Direct leak of 40 byte(s) in 1 object(s) allocated from:
    #0 0x7fc0559f1808 in __interceptor_malloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cc:144
    #1 0x7fc05520ee6e in alloc /home/aniruddhan/Downloads/calc/zmath.c:242
    #2 0x7fc055217b76 in zdiv /home/aniruddhan/Downloads/calc/zmath.c:1008
    #3 0x7fc05521870f in zmod /home/aniruddhan/Downloads/calc/zmath.c:1069
    #4 0x7fc055225a2c in zsquaremod /home/aniruddhan/Downloads/calc/zmod.c:122
    #5 0x7fc0552750ff in zrandom /home/aniruddhan/Downloads/calc/zrandom.c:2951
    #6 0x7fc055275961 in zrandomrange /home/aniruddhan/Downloads/calc/zrandom.c:3034
    #7 0x7fc054febc71 in f_random /home/aniruddhan/Downloads/calc/func.c:1230
    #8 0x7fc055081556 in builtinfunc /home/aniruddhan/Downloads/calc/func.c:13452
    #9 0x7fc0550eb6dd in o_call /home/aniruddhan/Downloads/calc/opcodes.c:2725
    #10 0x7fc0550f5b10 in calculate /home/aniruddhan/Downloads/calc/opcodes.c:4179
    #11 0x7fc0550eb628 in o_usercall /home/aniruddhan/Downloads/calc/opcodes.c:2716
    #12 0x7fc0550f5b10 in calculate /home/aniruddhan/Downloads/calc/opcodes.c:4179
    #13 0x7fc054f738aa in evaluate /home/aniruddhan/Downloads/calc/codegen.c:300
    #14 0x7fc054f7349d in getcommands /home/aniruddhan/Downloads/calc/codegen.c:230
    #15 0x7fc054f7336e in getcommands /home/aniruddhan/Downloads/calc/codegen.c:187
    #16 0x559b1cca636e in main /home/aniruddhan/Downloads/calc/calc.c:669
    #17 0x7fc053eab082 in __libc_start_main ../csu/libc-start.c:308

Direct leak of 36 byte(s) in 1 object(s) allocated from:
    #0 0x7fc0559f1808 in __interceptor_malloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cc:144
    #1 0x7fc05520ee6e in alloc /home/aniruddhan/Downloads/calc/zmath.c:242
    #2 0x7fc055217b76 in zdiv /home/aniruddhan/Downloads/calc/zmath.c:1008
    #3 0x7fc05521870f in zmod /home/aniruddhan/Downloads/calc/zmath.c:1069
    #4 0x7fc055225a2c in zsquaremod /home/aniruddhan/Downloads/calc/zmod.c:122
    #5 0x7fc0552750ff in zrandom /home/aniruddhan/Downloads/calc/zrandom.c:2951
    #6 0x7fc054febdfc in f_randombit /home/aniruddhan/Downloads/calc/func.c:1256
    #7 0x7fc055081556 in builtinfunc /home/aniruddhan/Downloads/calc/func.c:13452
    #8 0x7fc0550eb6dd in o_call /home/aniruddhan/Downloads/calc/opcodes.c:2725
    #9 0x7fc0550f5b10 in calculate /home/aniruddhan/Downloads/calc/opcodes.c:4179
    #10 0x7fc0550eb628 in o_usercall /home/aniruddhan/Downloads/calc/opcodes.c:2716
    #11 0x7fc0550f5b10 in calculate /home/aniruddhan/Downloads/calc/opcodes.c:4179
    #12 0x7fc054f738aa in evaluate /home/aniruddhan/Downloads/calc/codegen.c:300
    #13 0x7fc054f7349d in getcommands /home/aniruddhan/Downloads/calc/codegen.c:230
    #14 0x7fc054f7336e in getcommands /home/aniruddhan/Downloads/calc/codegen.c:187
    #15 0x559b1cca636e in main /home/aniruddhan/Downloads/calc/calc.c:669
    #16 0x7fc053eab082 in __libc_start_main ../csu/libc-start.c:308

SUMMARY: AddressSanitizer: 156 byte(s) leaked in 4 allocation(s).

The leak occurs in function zsetrandom where blum is reassigned before freeing. In fact just above the fix lies another patch of code that frees blum before assigning it. Therefore the patch frees blum before it is reassigned.

After this, the leaks are patched. I was able to verify that the leaks are gone and there is no double free. Let me know if the patch is helpful :)

lcn2 commented 8 months ago

Thank you very much @ashamedbit ‼️

We plan to release this change in the next version of calc.

lcn2 commented 8 months ago

We will give you credit, @ashamedbit, in the CHANGES file when calc v2.15.0.6 is released.

Your patch is much appreciated. Fixing memory leaks is VERY IMPORTANT to calc(1) as some run calc computations that take years to complete where even minor memory leaks can be deadly.