The change makes sure that SDL_vsnprintf() nul terminates if it is
using _vsnprintf() for the job.
I made this patch for Watcom, whose _vsnprintf() doesn't guarantee
nul termination. The preprocessor check can be extended to windows
in general too, if required.
Closes bug #3769.
Coriiander
Here is a minor correction for a non-breaking mistake in SDL_setenv for __WIN32__ platform. See below for details.
FILE:
"SDL/src/stdlib/SDL_getenv.c"
FUNCTION: (__WIN32__ platform)
int SDL_setenv(const char *name, const char *value, int overwrite)
CODE:
if (!overwrite) {
char ch = 0;
const size_t len = GetEnvironmentVariableA(name, &ch, sizeof (ch));
if (len > 0) {
return 0; /* asked not to overwrite existing value. */
}
}
WHAT'S WRONG:
The 3th argument to GetEnvironmentVariable (being DWORD nSize) must be the number of characters, not the number of bytes. SDL currently passes "the size of 1 char", rather "1". While it is non-breaking (1=1 after all), it is incorrect. Furthermore there is no need to specify the 2nd and 3th arguments at all.
CORRECTION 1: (corrected argument_
if (!overwrite) {
char ch = 0;
const size_t len = GetEnvironmentVariableA(name, &ch, 1);
if (len > 0) {
return 0; /* asked not to overwrite existing value. */
}
}
CORRECTION 2: (stripped of unneeded code)
if (!overwrite) {
if (GetEnvironmentVariableA(name, NULL, 0) > 0) {
return 0; /* asked not to overwrite existing value. */
}
}
Like other C runtimes, it should probably produce the string "(null)".
This bug probably only affected Windows, as most platforms use their standard
C runtime's snprintf().
Tristan
The internal SDL_vsnprintf implementation accesses memory outside buffer. The bug existed also inside the format (%) processing, which was fixed with Bug 3441.
But there is still an invalid access, if we do not have any format inside the source string and the destination string is shorter than the format string. You can use any string for this test, as long it is longer than the buffer.
Example:
va_list argList;
char buffer[4];
SDL_vsnprintf(buffer, sizeof(buffer), "Testing", argList);
The bug is located on the 'else' branch of the format char test:
while (*fmt) {
if (*fmt == '%') {
...
} else {
if (left > 1) {
*text = *fmt;
--left;
}
++fmt;
++text;
}
}
if (left > 0) {
*text = '\0';
}
As you can see that text is always incremented, even when left is already one. When then on the last lines, *text is assigned the NULL char, the pointer is located outside bounds.
Mark Pizzolato
On Windows with Visual Studio, when building SDL as a static library using the x86 (32bit) mode, several intrinsic operations are implemented in code in SDL_stdlib.c.
One of these, _allshr() is not properly implemented and fails for some input. As a result, some operations on 64bit data elements (long long) don't always work.
I classified this bug as a blocker since things absolutely don't work when the affected code is invoked. The affected code is only invoked when SDL is compiled in x86 mode on Visual Studio when building a SDL as a static library. This build environment isn't common, and hence the bug hasn't been noticed previously.
I reopened#2537 and mentioned this problem and provided a fix. That fix is provided again here along with test code which could be added to some of the SDL test code. This test code verifies that the x86 intrinsic routines produce the same results as the native x64 instructions which these routines emulate under the Microsoft compiler. The point of the tests is to make sure that Visual Studio x86 code produces the same results as Visual Studio x64 code. Some of the arguments (or boundary conditions) may produce different results on other compiler environments, so the tests really shouldn't be run on all compilers. The test driver only actually exercised code when the compiler defines _MSC_VER, so the driver can generically be invoked without issue.
Ryan C. Gordon
We still include iconv.h in SDL_stdinc.h, probably because this header might have referenced the native iconv functions and types directly. Since these are hidden behind a stable ABI now and never just a #define for the system iconv, we shouldn't need this header included from a public SDL header anymore, slowing down external apps compiles and pulling tons of stuff into the namespace.
Fixes Bugzilla #3441.
"When using internal SDL_vsnprintf(), and source string length is greater
than destination, the final NULL char will be written beyond destination size.
Primary issue that is SDL_strlcpy returns length of source string
(SDL_PrintString()), not how much is written to destination. The destination
ptr is then incremented by this length before the sanity check is done.
Destination string is properly terminated, but an extra NULL char will be
written beyond destination buffer length.
Patch used internally is attached which fixes primary issue with SDL_strlcpy()
in SDL_PrintString() and adjusts sanity checks to increment destination ptr
safely."
