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optimize_clear_loop bail early if instructions struct too small #8

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optimize_clear_loop bail early if instructions struct too small #8

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rwhitworth
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Helps avoid #7

@rwhitworth rwhitworth mentioned this pull request Jul 8, 2017
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@julianneswinoga
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In what situation does the original code cause an error?

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Example input: input.gz

It fixes this error as reported by valgrind:

==943710== Invalid read of size 1
==943710==    at 0x405722: optimize_clear_loop (optimize.c:77)
==943710==    by 0x401AA1: main (yabfc.c:136)
==943710==  Address 0x56df9b8 is 0 bytes after a block of size 8 alloc'd
==943710==    at 0x4C2DDCF: realloc (vg_replace_malloc.c:785)
==943710==    by 0x4018E1: main (yabfc.c:118)

julianneswinoga
julianneswinoga requested changes Jul 9, 2017
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optimize.c
@@ -70,7 +70,9 @@ bool optimize_compress_PTR(INSTRUCTIONS *instructions, int *position, CODE *code
bool optimize_clear_loop(INSTRUCTIONS *instructions, int *position, CODE *code) {
if (globalOptions.optimize < 2) // Only do on optimization level 2 and higher
return false;

if (instructions->size - (*position) < 3)
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Can you change the 3 to be based on the number of characters being checked? I.e. sizeof(clearLoop) - 1?

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@julianneswinoga julianneswinoga julianneswinoga requested changes

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@rwhitworth @julianneswinoga