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Avoiding undefined behaviors (nit picking)

This commit is contained in:
Daniel Lemire 2018-08-14 17:52:15 -04:00
parent 0c8b4a9f12
commit 01ea7996b2
2 changed files with 14 additions and 5 deletions
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1
main.cpp
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@ -302,5 +302,6 @@ int main(int argc, char * argv[]) {
free(pj.structurals);
free(p.first);
delete[] pj.structural_indexes;
delete pj_ptr;
return 0;
}

18
stage4_shovel_machine.cpp
View File

@ -1,5 +1,6 @@
#include <x86intrin.h>
#include <assert.h>
#include <cstring>
#include "common_defs.h"
#include "simdjson_internal.h"
@ -151,8 +152,9 @@ really_inline bool handle_unicode_codepoint(const u8 ** src_ptr, u8 ** dst_ptr)
u32 tmp = _pdep_u32(code_point, UTF_PDEP_MASK[utf_bytes]) | UTF_OR_MASK[utf_bytes];
// swap and move to the other side of the register
tmp = __builtin_bswap32(tmp);
tmp >>= (4 - utf_bytes) * 8;
**(u32 **)dst_ptr = tmp;
tmp >>= ((4 - utf_bytes) * 8) & 31;// if utf_bytes, this could become a shift by 32, hence the mask with 31
// use memcpy to avoid undefined behavior:
std::memcpy(*(u32 **)dst_ptr,&tmp,sizeof(u32)); //**(u32 **)dst_ptr = tmp;
*dst_ptr += utf_bytes;
return true;
}
@ -519,21 +521,27 @@ bool shovel_machine(const u8 * buf, size_t len, ParsedJson & pj) {
case 't': {
u32 offset = pj.tape[j] & 0xffffffffffffffULL;
const u8 * loc = buf + offset;
error_sump |= ((*(const u64 *)loc) & mask4) ^ tv;
u64 locval;// we want to avoid unaligned 64-bit loads (undefined in C/C++)
std::memcpy(&locval,loc,sizeof(u64));
error_sump |= (locval & mask4) ^ tv;
error_sump |= is_not_structural_or_whitespace(loc[4]);
break;
}
case 'f': {
u32 offset = pj.tape[j] & 0xffffffffffffffULL;
const u8 * loc = buf + offset;
error_sump |= ((*(const u64 *)loc) & mask5) ^ fv;
u64 locval;// we want to avoid unaligned 64-bit loads (undefined in C/C++)
std::memcpy(&locval,loc,sizeof(u64));
error_sump |= (locval & mask5) ^ fv;
error_sump |= is_not_structural_or_whitespace(loc[5]);
break;
}
case 'n': {
u32 offset = pj.tape[j] & 0xffffffffffffffULL;
const u8 * loc = buf + offset;
error_sump |= ((*(const u64 *)loc) & mask4) ^ nv;
u64 locval;// we want to avoid unaligned 64-bit loads (undefined in C/C++)
std::memcpy(&locval,loc,sizeof(u64));
error_sump |= (locval & mask4) ^ nv;
error_sump |= is_not_structural_or_whitespace(loc[4]);
break;
}