pgm_read_float alignment issue when reading from an array of floats

[maxint-rd]

Basic Infos

• This issue complies with the issue POLICY doc.
• I have read the documentation at readthedocs and the issue is not addressed there.
• I have tested that the issue is present in current master branch (aka latest git).
• I have searched the issue tracker for a similar issue.
• If there is a stack dump, I have decoded it.
• I have filled out all fields below.

Platform

• Hardware: [ESP-12E]
• Core Version: [2.5.2 (may-20-2019, installed via board manager]
• Development Env: [Arduino IDE]
• Operating System: [Windows]

Settings in IDE

• Module: [Generic ESP8266 Module]
• Flash Mode: [dout (compatible)]
• Flash Size: [4MB (3M SPIFFS)]
• lwip Variant: [v2 Lower Memory]
• Reset Method: [nodemcu]
• Flash Frequency: [40Mhz]
• CPU Frequency: [80Mhz]
• Upload Using: [SERIAL]
• Upload Speed: [512000] (serial upload only)

Problem Description

My MmlMusic library reads tone frequencies as float values from a PROGMEM array. It worked fine for ESP8266 core version 2.5.0, but failed in cores version 2.5.1 and 2.5.2
Using the defines mentioned in issue #5628 fixed the problem, but I guess it's better to use pgm_read_float_aligned() as mentioned in pull #5692 . The default define uses the _unaligned version, but as I noticed then the floats are not properly read from the PROGMEM array.
This issue is about compatibility. The Arduino library works fine on ATmega and ATtiny MCU's.
See the sketch below for more detailed info.

MCVE Sketch

#include <Arduino.h>

const float aftTest[] = {1.23, 2.34, 3.45};
const float aftTestPGM[] PROGMEM = {1.23, 2.34, 3.45};

void setup() {
  float ftTest=0.0;
  Serial.begin(115200);  
  Serial.println("\nTesting pgm_read_float");
  Serial.print("mem array:");
  ftTest=aftTest[1];
  Serial.println(ftTest);       // should print 2.34
// uncomment to fix pgm_read_float issue
//  #define pgm_read_float(addr)            pgm_read_float_aligned(addr)
  ftTest = pgm_read_float(&aftTestPGM[1]);
  Serial.print("pgm array:");
  Serial.println(ftTest);       // should print 2.34, but prints silly large number
}

void loop() {
}

Debug Messages

Testing pgm_read_float (unfixed)
mem array:2.34
pgm array:1075167872.00

Testing pgm_read_float (fixed)
mem array:2.34
pgm array:2.34