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  • Good that you found it - and thank you for the caution about #define and strings. Note that you should have used static const char TXTCOMPARE1[] = "Sample Text 1";, and also that if (p) { p =NULL; } wastes an if. Just do p = NULL; - it's smaller and faster. Oh, and completely unnecessary. p is about to disappear anyway when it goes out of scope: no need to zero it out. Commented Sep 11, 2016 at 5:51
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    Another problem was that there was no NULL terminated character at the end of the #define statement - that's not true. It's hard to tell from your snippet but a #define just does a textual replacement. Commented Oct 12, 2016 at 1:01
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    There is no need to malloc memory for p, just declare it as a char *p = NULL; strstr then returns a pointer to the existing strings. All the malloc line is doing is leaking memory. Commented Jan 10, 2017 at 9:32
  • The statement "This is because the compiler applies the text every time they appear in the code, so it uses up a lot more memory" is wrong. No matter what declaration you use (#define, const char), the memory usage is the same. The C compiler take care of reusing the string when it appears for second time. Wrote a little test program and see how much RAM/program memory it use. Commented Aug 8, 2017 at 19:37