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Stop arrayprinter from sizing its stack buffer from the input

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printHex and printDec built a variable length array of (size + 1) * 7 + 1 and
size * 4 + 1 + lines bytes respectively, on the stack, from the caller's
buffer size. Nothing bounded that against the stack it ran on.

This reset an iOBC on the flatsat. A CFDP uplink driven without inter packet
spacing filled the USLP receive buffer with about 12 KB in one 300 ms cycle,
a frame parse error asked for the serial stream to be dumped, and printHex
tried to place an 84 KB array on an 8 KB task stack. FreeRTOS caught it as
STACK OVERFLOW DETECTED in USLP_RX and restarted the OBC.

The trigger needs a parse error, so it hid for as long as the link stayed
clean: USLP_RX sat at 800 bytes of its 8 KB, and the first corrupted frame
with a full receive buffer behind it was fatal.

Emit the output in fixed 128 byte chunks instead, flushing as it is built.
The rendered text is unchanged - verified byte for byte against the previous
implementation for sizes 0 to 4096 and several line widths, including the
line break boundaries.

printBin was already safe.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N4eBFnanCACYWdKCzhHMcC
This commit is contained in:
Tobias Baumgartl
2026-09-16 12:02:57 +02:00
co-authored by Claude Opus 5
parent e256fa4b92
commit 844faf850f
1 changed files with 35 additions and 25 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/fsfw/globalfunctions/arrayprinter.cpp
+35 -25
View File
@@ -56,26 +56,33 @@ void arrayprinter::printHex(const uint8_t *data, size_t size, size_t maxCharPerL
std::cout << std::dec << std::setfill(' ');
std::cout << "]" << std::endl;
#else
// General format: 0x01, 0x02, 0x03 so it is number of chars times 6
// plus line break plus small safety margin.
char printBuffer[(size + 1) * 7 + 1] = {};
#if FSFW_DISABLE_PRINTOUT == 0
// Emitted in fixed size chunks. This used to size one buffer from the input - a variable length
// array of (size + 1) * 7 + 1 bytes on the stack - which is unusable for the sizes this is
// actually called with: dumping a 12 KB receive buffer asks for 84 KB of stack, and overflowed
// an 8 KB task on the iOBC as soon as a frame parse error made it dump one. The output is
// unchanged, it is just flushed as it is built.
constexpr size_t CHUNK_LEN = 128;
// An entry appends at most two hex digits, a separator and a line break.
constexpr size_t MAX_ENTRY_LEN = 4;
char printBuffer[CHUNK_LEN] = {};
size_t currentPos = 0;
printf("hex [");
for (size_t i = 0; i < size; i++) {
// To avoid buffer overflows.
if (sizeof(printBuffer) - currentPos <= 7) {
break;
if (currentPos + MAX_ENTRY_LEN >= CHUNK_LEN) {
printf("%s", printBuffer);
printBuffer[0] = '\0';
currentPos = 0;
}
currentPos += snprintf(printBuffer + currentPos, 6, "%02x", data[i]);
currentPos += snprintf(printBuffer + currentPos, CHUNK_LEN - currentPos, "%02x", data[i]);
if (i < size - 1) {
currentPos += sprintf(printBuffer + currentPos, ",");
currentPos += snprintf(printBuffer + currentPos, CHUNK_LEN - currentPos, ",");
if ((i + 1) % maxCharPerLine == 0) {
currentPos += sprintf(printBuffer + currentPos, "\n");
currentPos += snprintf(printBuffer + currentPos, CHUNK_LEN - currentPos, "\n");
}
}
}
#if FSFW_DISABLE_PRINTOUT == 0
printf("hex [%s]\n", printBuffer);
printf("%s]\n", printBuffer);
#endif /* FSFW_DISABLE_PRINTOUT == 0 */
#endif
}
@@ -98,27 +105,30 @@ void arrayprinter::printDec(const uint8_t *data, size_t size, size_t maxCharPerL
}
std::cout << "]" << std::endl;
#else
// General format: 32,243,-12 so it is number of chars times 4
// plus line break plus small safety margin.
uint16_t expectedLines = ceil((double)size / maxCharPerLine);
char printBuffer[size * 4 + 1 + expectedLines] = {};
#if FSFW_DISABLE_PRINTOUT == 0
// Chunked for the same reason as printHex above: the buffer used to be a variable length array
// sized from the input.
constexpr size_t CHUNK_LEN = 128;
// An entry appends at most three digits, a separator and a line break.
constexpr size_t MAX_ENTRY_LEN = 5;
char printBuffer[CHUNK_LEN] = {};
size_t currentPos = 0;
printf("dec [");
for (size_t i = 0; i < size; i++) {
// To avoid buffer overflows.
if (sizeof(printBuffer) - currentPos <= 4) {
break;
if (currentPos + MAX_ENTRY_LEN >= CHUNK_LEN) {
printf("%s", printBuffer);
printBuffer[0] = '\0';
currentPos = 0;
}
currentPos += snprintf(printBuffer + currentPos, 4, "%d", data[i]);
currentPos += snprintf(printBuffer + currentPos, CHUNK_LEN - currentPos, "%d", data[i]);
if (i < size - 1) {
currentPos += sprintf(printBuffer + currentPos, ",");
currentPos += snprintf(printBuffer + currentPos, CHUNK_LEN - currentPos, ",");
if ((i + 1) % maxCharPerLine == 0) {
currentPos += sprintf(printBuffer + currentPos, "\n");
currentPos += snprintf(printBuffer + currentPos, CHUNK_LEN - currentPos, "\n");
}
}
}
#if FSFW_DISABLE_PRINTOUT == 0
printf("dec [%s]\n", printBuffer);
printf("%s]\n", printBuffer);
#endif /* FSFW_DISABLE_PRINTOUT == 0 */
#endif
}