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games/NXDoom: Parse configuration one line at a time.

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Read each physical configuration line independently so malformed or truncated input cannot consume a following setting as its value. Discard overlong lines and retain defaults for incomplete entries.

Assisted-by: Codex:gpt-5
Signed-off-by: aviralgarg05 <gargaviral99@gmail.com>
This commit is contained in:
aviralgarg05 2026-07-23 21:04:20 +05:30
parent b51959ea77
commit c4bf636057
1 changed files with 12 additions and 42 deletions
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54
games/NXDoom/src/m_config.c
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@ -2082,6 +2082,7 @@ static void load_default_collection(default_collection_t *collection)
default_t *def;
char defname[80];
char strparm[100];
char line[256];
/* read the file in, overriding any set defaults */
@ -2096,51 +2097,28 @@ static void load_default_collection(default_collection_t *collection)
return;
}
for (; ; )
while (fgets(line, sizeof(line), f) != NULL)
{
int nmatched;
long before;
strparm[0] = '\0';
/* Checking feof() to decide whether to keep looping (rather than
* acting on fscanf()'s own return value) is the classic C bug: on
* a config file whose bytes don't line up with "%s %[^\n]\n" at
* all - e.g. leftover binary/corrupted content from a previous
* write - fscanf() can fail a conversion without the stream ever
* reaching EOF, and feof() has no way to know that. That left
* this loop spinning forever parsing nothing, which is exactly
* what made a corrupted default.cfg hang the whole game at
* startup instead of just skipping the bad file.
*
* Terminating off EOF/error from fscanf() itself closes the
* common case, but a failed conversion is only guaranteed to
* consume nothing - it is not guaranteed to have advanced the
* stream either, so a byte sequence that never matches "%s" but
* also never reports EOF/error could still spin without making
* progress. Track the file position directly and force one
* byte of forward progress (or bail out) if a scan attempt
* didn't move it, so corrupt/binary content can only ever cost
* one pass over the file, never an infinite loop.
/* Parse one physical line at a time. fscanf() with whitespace in
* its format can consume the next line as a missing value.
*/
before = ftell(f);
nmatched = fscanf(f, "%79s %99[^\n]\n", defname, strparm);
if (nmatched == EOF)
if (strchr(line, '\n') == NULL &&
strlen(line) == sizeof(line) - 1)
{
break;
}
int ch;
if (nmatched < 1)
{
if (ftell(f) == before && fgetc(f) == EOF)
while ((ch = fgetc(f)) != '\n' && ch != EOF)
{
break;
}
/* This line doesn't match */
continue;
}
if (sscanf(line, "%79s %99[^\n]", defname, strparm) != 2)
{
continue;
}
@ -2175,14 +2153,6 @@ static void load_default_collection(default_collection_t *collection)
memmove(strparm, strparm + 1, sizeof(strparm) - 1);
}
/* A line with a name but no (or an unparsable) value - e.g. a
* config file left truncated by an unclean shutdown mid-write -
* must not silently override this variable's compiled-in default
* with a bogus zero/empty value. This is what let a corrupted
* "screenblocks" line (empty value) through as screenblocks=0,
* which fed a divide-by-zero straight into the renderer.
*/
if (strparm[0] == '\0')
{
continue;