add more text to the readme

This commit is contained in:
Martin Errenst 2017-08-27 14:23:19 +02:00
parent e5b52949b2
commit 25115cb15d
2 changed files with 16 additions and 6 deletions

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== Motivation
Print as much information about the build process as you can get from within the binary.
Espacially, compiler flags - they are quite important when comparing performance.
The information should be included in the binary, so it can't be lost and is right next to, for example, a benchmark result.
So there's no chance to mix up different flags.
== Other options
Another option would be -g -grecord-gcc-switches and search for DW_AT_producer.
Sadly, this doesn't produce the wanted information with clang:
* clang++: DW_AT_producer : (indirect string, offset: 0x0): clang version 3.9.1 (tags/RELEASE_391/final)
* g++: DW_AT_producer : (indirect string, offset: 0x37): GNU C++ 4.9.4 -mtune=generic -march=x86-64 -g -O3 -frecord-gcc-switches -fstack-protector-strong
Passing the CPPFLAGS and so on as -DMY_FLAGS=.... to the compiler call will not include some information set by the compiler itself (compare the parameters set in the Makefile with the printed output).
== Known limitations
* Works only with GCC for now.

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Another option would be -g -grecord-gcc-switches and search for DW_AT_producer.
Sadly, this doesn't produce the wanted information with clang:
clang++: DW_AT_producer : (indirect string, offset: 0x0): clang version 3.9.1 (tags/RELEASE_391/final)
g++: DW_AT_producer : (indirect string, offset: 0x37): GNU C++ 4.9.4 -mtune=generic -march=x86-64 -g -O3 -frecord-gcc-switches -fstack-protector-strong
Passing the CPPFLAGS and so on as -DMY_FLAGS=.... to the compiler call will not include some information set by the compiler itself (compare the parameters set in the Makefile with the printed output).