WebServer serveStatic () can cause LoadProhibited exception in _svfprintf_r

[timr49]

Hardware:

Board: Sparkfun ESP32Thing
Core Installation version: 2.0.0-rc1
IDE name: Arduino IDE 1.8.5
Flash Frequency: 80Mhz
PSRAM enabled: ?PSRAM?
Upload Speed: 921600
Computer OS: Mac OSX 11.5.1

Description:

Using a Core Debug Level of Verbose and the WebServer serveStatic() function with the default value of nullptr for its cache_header argument, results in a LoadProhibited exception in _svfprintf_r().
This is because serveStatic() calls log_v() with cache_header corresponding to a "%s" in its format but without checking that cache_header is not nullptr, and then logv() (indirectly) calls _svfprintf_r().
On the other hand, with a Core Debug Level other than Verbose, this does not occur.

Sketch: (leave the backquotes for code formatting)

//Change the code below by your sketch
[code]
#include <WiFi.h>
#include <WebServer.h>
#include <SPIFFS.h>
#include "secret.h" // for definitions of MySSID and MyPASSWORD

WebServer server;

void setup() {
  // put your setup code here, to run once:
  // serial
  Serial.begin(115200);
  while (!Serial)
    delay(100);
  Serial.println("setting up");

  // wifi
  WiFi.begin(MySSID, MyPASSWORD); // as defined in "secret.h"
  while (!WiFi.isConnected())
  {
    Serial.print('.');
    delay(100);
  }
  Serial.println();
  Serial.print("connected to "); Serial.print(WiFi.SSID());
  Serial.print(" with address "); Serial.println(WiFi.localIP());

  // www server
  server.begin();
  SPIFFS.begin();
  server.serveStatic("/index.htm", SPIFFS, "/index.htm");

  Serial.println("listening");
}

void loop() {
  // put your main code here, to run repeatedly:
  server.handleClient();
}
[/code]```

### Debug Messages:

ets Jun 8 2016 00:22:57

rst:0x10 (RTCWDT_RTC_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:1
load:0x3fff0030,len:1100
ho 0 tail 12 room 4
load:0x40078000,len:12752
load:0x40080400,len:3092
entry 0x400805e4
[����$$HLW+QW⸮Y.&⸮KZX⸮K,]⸮,'⸮LLW⸮⸮Y](]⸮⸮equencyMhz(): PLL: 480 / 2 = 240 Mhz, APB: 80000000 Hz
⸮⸮Y]⸮Z⸮�⸮�⸮H⸮[ 63][D][WiFiGeneric.cpp:808] _eventCallback(): Arduino Event: 0 - WIFI_READY
[ 160][V][WiFiGeneric.cpp:96] set_esp_interface_ip(): Configuring Station static IP: 0.0.0.0, MASK: 0.0.0.0, GW: 0.0.0.0
[ 159][V][WiFiGeneric.cpp:272] _arduino_event_cb(): STA Started
[ 166][D][WiFiGeneric.cpp:808] _eventCallback(): Arduino Event: 2 - STA_START
.....................[ 2266][V][WiFiGeneric.cpp:284] _arduino_event_cb(): STA Connected: SSID: MOBILE3, BSSID: 00:1e:42:19:71:d9, Channel: 11, Auth: WPA2_PSK
[ 2267][D][WiFiGeneric.cpp:808] _eventCallback(): Arduino Event: 4 - STA_CONNECTED
.[ 2338][V][WiFiGeneric.cpp:294] _arduino_event_cb(): STA Got New IP:192.168.10.157
[ 2338][D][WiFiGeneric.cpp:808] _eventCallback(): Arduino Event: 7 - STA_GOT_IP
[ 2342][D][WiFiGeneric.cpp:857] _eventCallback(): STA IP: 192.168.10.157, MASK: 255.255.255.0, GW: 192.168.10.3

connected to MOBILE3 with address 192.168.10.157
Guru Meditation Error: Core 1 panic'ed (LoadProhibited). Exception was unhandled.

Core 1 register dump:
PC : 0x40089275 PS : 0x00060630 A0 : 0x8014f16c A1 : 0x3ffb2340
A2 : 0x00000000 A3 : 0xfffffffc A4 : 0x000000ff A5 : 0x0000ff00
A6 : 0x00ff0000 A7 : 0xff000000 A8 : 0x00000000 A9 : 0x00000000
A10 : 0x00000000 A11 : 0x3ffb2543 A12 : 0x00000000 A13 : 0x3ffdd3f0
A14 : 0x3ffc2204 A15 : 0x00000011 SAR : 0x00000004 EXCCAUSE: 0x0000001c
EXCVADDR: 0x00000000 LBEG : 0x40089275 LEND : 0x40089285 LCOUNT : 0xffffffff

Backtrace:0x40089272:0x3ffb23400x4014f169:0x3ffb2350 0x4015634e:0x3ffb2660 0x4015638a:0x3ffb26f0 0x400dcdc9:0x3ffb2730 0x400dab16:0x3ffb2790 0x400d287e:0x3ffb27d0 0x400de5ab:0x3ffb2820

ELF file SHA256: 0000000000000000

Rebooting...
ets Jun 8 2016 00:22:57

EspExceptionDecoder ...

PC: 0x40089275
EXCVADDR: 0x00000000

Decoding stack results
0x4014f169: _svfprintf_r at /builds/idf/crosstool-NG/.build/HOST-x86_64-apple-darwin12/xtensa-esp32-elf/src/newlib/newlib/libc/stdio/vfprintf.c line 1528
0x4015634e: _vsnprintf_r at /builds/idf/crosstool-NG/.build/HOST-x86_64-apple-darwin12/xtensa-esp32-elf/src/newlib/newlib/libc/stdio/vsnprintf.c line 70
0x4015638a: vsnprintf at /builds/idf/crosstool-NG/.build/HOST-x86_64-apple-darwin12/xtensa-esp32-elf/src/newlib/newlib/libc/stdio/vsnprintf.c line 40
0x400dcdc9: log_printf at /Users/tim/Library/Arduino15/packages/esp32/hardware/esp32/2.0.0-rc1/cores/esp32/esp32-hal-uart.c line 633
0x400dab16: WebServer::serveStatic(char const*, fs::FS&, char const*, char const*) at /Users/tim/Library/Arduino15/packages/esp32/hardware/esp32/2.0.0-rc1/libraries/WebServer/src/detail/RequestHandlersImpl.h line 72
0x400d287e: setup() at /Users/tim/Repositories/sam/src/Arduino/IssueLOGV/IssueLOGV.ino line 30
0x400de5ab: loopTask(void*) at /Users/tim/Library/Arduino15/packages/esp32/hardware/esp32/2.0.0-rc1/cores/esp32/main.cpp line 35

[VojtechBartoska]

For some reason issue wasn't closed with given PR. I'm closing manually.