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Reduce stack usage by Print::printf

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Print::printf would allocate 1460 bytes on the stack, which in some cases would overflow the stack. Additionally it didn't handle (rare) cases when vsnprintf needed a buffer longer than 1460 bytes. This change makes default stack-allocated buffer 64 bytes long, and checks the result returned by vsnprintf. If a buffer longer than 64 bytes is needed, it is allocated on the heap.
This commit is contained in:
Ivan Grokhotkov 2016-02-26 18:31:50 +03:00
parent f28c5be479
commit d891704c1e
1 changed files with 20 additions and 7 deletions
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19
cores/esp8266/Print.cpp
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@ -47,10 +47,23 @@ size_t ICACHE_FLASH_ATTR Print::write(const uint8_t *buffer, size_t size) {
size_t Print::printf(const char *format, ...) {
va_list arg;
va_start(arg, format);
char temp[1460];
size_t len = ets_vsnprintf(temp, 1460, format, arg);
len = print(temp);
char temp[64];
char* buffer = temp;
size_t len = vsnprintf(temp, sizeof(temp), format, arg);
va_end(arg);
if (len > sizeof(temp) - 1) {
buffer = new char[len + 1];
if (!buffer) {
return 0;
}
va_start(arg, format);
vsnprintf(buffer, len + 1, format, arg);
va_end(arg);
}
len = write((const uint8_t*) buffer, len);
if (buffer != temp) {
delete[] buffer;
}
return len;
}