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discontinue use of alloca

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NetBSD emits:
warning: Warning: reference to the libc supplied alloca(3); this most likely will not work. Please use the compiler provided version of alloca(3), by supplying the appropriate compiler flags (e.g. not -std=c89).

and man 3 alloca says:

       Normally,  gcc(1)  translates  calls  to  alloca()  with  inlined code.  This is not done when either the -ansi, -std=c89, -std=c99, or the
       -std=c11 option is given and the header <alloca.h> is not included.  Otherwise, (without an -ansi or -std=c* option) the glibc  version  of
       <stdlib.h> includes <alloca.h> and that contains the lines:

           #ifdef  __GNUC__
           #define alloca(size)   __builtin_alloca (size)
           #endif

It looks like alloca is a bad idea in modern C/C++, so we use
VLAs for C and std::vector for C++.
This commit is contained in:
moneromooo-monero 2019-02-23 12:00:41 +00:00
parent 31bdf7bd11
commit 7d88d8f27c
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GPG key ID: 686F07454D6CEFC3
2 changed files with 4 additions and 14 deletions
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14
src/crypto/tree-hash.c
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@ -34,15 +34,6 @@
#include "hash-ops.h"
#ifdef _MSC_VER
#include <malloc.h>
#elif !defined(__FreeBSD__) && !defined(__OpenBSD__) && !defined(__DragonFly__) \
&& !defined(__NetBSD__)
#include <alloca.h>
#else
#include <stdlib.h>
#endif
/***
* Round to power of two, for count>=3 and for count being not too large (as reasonable for tree hash calculations)
*/
@ -91,9 +82,8 @@ void tree_hash(const char (*hashes)[HASH_SIZE], size_t count, char *root_hash) {
size_t cnt = tree_hash_cnt( count );
char (*ints)[HASH_SIZE];
size_t ints_size = cnt * HASH_SIZE;
ints = alloca(ints_size); memset( ints , 0 , ints_size); // allocate, and zero out as extra protection for using uninitialized mem
char ints[cnt][HASH_SIZE];
memset(ints, 0 , sizeof(ints)); // zero out as extra protection for using uninitialized mem
memcpy(ints, hashes, (2 * cnt - count) * HASH_SIZE);