readme: clarify CFLAGS prepending/overriding

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Manuel Pégourié-Gonnard 2017-12-28 09:14:47 +01:00
parent b89c472ad5
commit 05c92715be

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@ -76,7 +76,9 @@ You'll still be able to run a much smaller set of tests with:
In order to build for a Windows platform, you should use `WINDOWS_BUILD=1` if the target is Windows but the build environment is Unix-like (for instance when cross-compiling, or compiling from an MSYS shell), and `WINDOWS=1` if the build environment is a Windows shell (for instance using mingw32-make) (in that case some targets will not be available).
Setting the variable `SHARED` in your environment will build shared libraries in addition to the static libraries. Setting `DEBUG` gives you a debug build. You can override `CFLAGS` and `LDFLAGS` by setting them in your environment or on the make command line; if you do so, essential parts such as `-I` will still be preserved. Warning options may be overridden separately using `WARNING_CFLAGS`.
Setting the variable `SHARED` in your environment will build shared libraries in addition to the static libraries. Setting `DEBUG` gives you a debug build. You can override `CFLAGS` and `LDFLAGS` by setting them in your environment or on the make command line; compiler warning options may be overridden separately using `WARNING_CFLAGS`. Some directory-specific options (for example, `-I` directives) are still preserved.
Please note that setting `CFLAGS` overrides its default value of `-O2` and setting `WARNING_CFLAGS` overrides its default value (starting with `-Wall -W`), so it you just want to add some warning options to the default ones, you can do so by setting `CFLAGS=-O2 -Werror` for example. Setting `WARNING_CFLAGS` is useful when you want to get rid of its default content (for example because your compiler doesn't accept `-Wall` as an option). Directory-specific options cannot be overriden from the command line.
Depending on your platform, you might run into some issues. Please check the Makefiles in `library/`, `programs/` and `tests/` for options to manually add or remove for specific platforms. You can also check [the Mbed TLS Knowledge Base](https://tls.mbed.org/kb) for articles on your platform or issue.
@ -154,6 +156,10 @@ You can not make the desired change:
CC=your_cc cmake .
make
Regarding variables, also note that if you set CFLAGS when invoking cmake,
your value of CFLAGS doesn't override the content provided by cmake (depending
on the build mode as seen above), it's merely prepended to it.
### Microsoft Visual Studio
The build files for Microsoft Visual Studio are generated for Visual Studio 2010.