From: Alexandre Raymond <alexandre.j.raymond@gmail.com>
To: newlib@sourceware.org
Subject: Issue with sscanf not parsing correctly
Date: Sun, 15 Aug 2021 22:38:11 -0400 [thread overview]
Message-ID: <CAD4yBunQ0L0+=mYr07QADRR8e2bnTLvZAHFc0v2=qUsmTetxfg@mail.gmail.com> (raw)
Greetings!
I have been developing on a Teensy 4.1 platform, which I'm told uses
newlib under the hood, and encountered a strange issue with sscanf,
where different parameter orderings yield different results with
stdint types.
Here is a minimal code sample which exhibits the issue:
---8<---
#include <stdio.h>
#include <stdint.h>
void setup() {
uint8_t i2c_addr = 1;
uint16_t mem_addr = 1;
uint8_t len = 1;
int ret;
Serial.println(String(i2c_addr) + "," + String(mem_addr) + "," +
String(len));
//prints: 1,1,1
const char *cmd = "1 2 3\n";
// This is the order I intended to scan the string in
ret = sscanf(cmd, "%hhu %hu %hhu", &i2c_addr, &mem_addr, &len);
Serial.println(String(ret) + "- " + String(i2c_addr) + "," +
String(mem_addr) + "," + String(len));
// prints: 3- 1,0,3
// I just swap the order of the target variables around
ret = sscanf(cmd, "%hhu %hhu %hu", &i2c_addr, &len, &mem_addr);
Serial.println(String(ret) + "- " + String(i2c_addr) + "," +
String(len) + "," + String(mem_addr));
// prints: 3- 1,2,3
}
void loop() { }
--8<---
Would you have any idea what may be causing this?
Thanks in advance for your help!
Alexandre
next reply other threads:[~2021-08-16 2:38 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-16 2:38 Alexandre Raymond [this message]
2021-08-16 16:42 ` Keith Packard
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