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Fix strict aliasing violations

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Compiler only guarantees proper accesses to variables when using
variable's native type or `char` (i.e. single byte type) [1].

This commit fixes violations of this rule. In most cases changing code
to a simple cast was enough, some required a bit deeper modifications.

This fixes #2596.

[1] http://blog.qt.io/blog/2011/06/10/type-punning-and-strict-aliasing/
This commit is contained in:
Michał Janiszewski
2015-12-31 09:16:44 +01:00
parent db95b3ada3
commit 8a5d066efe
18 changed files with 98 additions and 77 deletions
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17
src/hook.c
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@@ -30,6 +30,14 @@ void* g_hooktableaddress = 0;
int g_hooktableoffset = 0;
int g_maxhooks = 1000;
// This macro writes a little-endian 4-byte long value into *data
// It is used to avoid type punning.
#define write_address_strictalias(data, addr) \
*(data + 0) = ((addr) & 0x000000ff) >> 0; \
*(data + 1) = ((addr) & 0x0000ff00) >> 8; \
*(data + 2) = ((addr) & 0x00ff0000) >> 16; \
*(data + 3) = ((addr) & 0xff000000) >> 24;
void hookfunc(int address, int newaddress, int stacksize, int registerargs[], int registersreturned, int eaxDestinationRegister)
{
int i = 0;
@@ -118,7 +126,9 @@ void hookfunc(int address, int newaddress, int stacksize, int registerargs[], in
}
data[i++] = 0xE8; // call
*((int *)&data[i]) = (newaddress - address - i - 4); i += 4;
write_address_strictalias(&data[i], newaddress - address - i - 4);
i += 4;
// returnlocation:
@@ -220,7 +230,10 @@ void addhook(int address, int newaddress, int stacksize, int registerargs[], int
char data[9];
int i = 0;
data[i++] = 0xE9; // jmp
*((int *)&data[i]) = hookaddress - address - i - 4; i += 4;
write_address_strictalias(&data[i], hookaddress - address - i - 4);
i += 4;
data[i++] = 0xC3; // retn
#ifdef _WIN32
WriteProcessMemory(GetCurrentProcess(), (LPVOID)address, data, i, 0);