Error: ‘malloc’ was not declared in this scope when using malloc() in c++
1. Handwriting errors.
2. No reference to the appropriate library.
Solution: Introduce stdlib.h

#include<stdlib.h>

guess is that there is a solution, not try: https://blog.csdn.net/u012197749/article/details/79687899 Read More: c++ error: ‘malloc’ was not declared in this scope g++ error: ‘printf’ was not declared in this scope Analysis of the causes of errors in G + + compilation “was not declared in this scope”“ error: ‘NULL’ was not declared in this scope error: ‘atoi’ was not declared in this scope error: ‘exit’ was not declared in this scope error: `cout’ was not declared in this scope error: ‘memcpy’ was not declared in this scope error: ‘CV_BGR2GRAY’ was not declared in this scope [Error] ‘sort’ was not declared in this scope Arduino ide 1.6.9 problems encountered error:’TKD2′ was not declared in this scope error: ‘vector‘ was not declared in this scope| Error:‘itoa’ was not declared in this scope Code::Blocks 12.11 error: ‘nullptr’ was not declared in this scope&GNU GCC -std=gnu++0x Code:: blocks prompt nullptr’s was not declared in this scope error: ‘stoi’ was not declared in this scope linux (Fixed) “Error: ` cout ‘was not declared in this scope” Arduino reports an error when writing a custom library file to solve the problem of not name of type, not declared in this scope Abnormal crash of APP startup — pointer being free was not allocated * * set a breakpoint in malloc_ error_ break to debug Error c2951: template declaration can only be used at the global, namespace, or class scope. Error c2598: link specification must be at the global scope