Analyse following RPM build log snippet. Describe contents accurately, without speculation or suggestions for resolution.            
Your analysis must be as concise as possible, while keeping relevant information intact.
Snippet: 
GNU M4 1.4.6 or later is required; 1.4.16 or newer is recommended.
GNU M4 1.4.15 uses a buggy replacement strstr on some systems.
Glibc 2.9 - 2.12 and GNU M4 1.4.11 - 1.4.15 have another strstr bug
Reasons are given for why various M4 versions are not acceptable.