Cannot view std::string when compiled with clang

As ks1322 mentioned, this is because clang has decided not to emit debug information for libstc++.

You can force clang to do so by providing the following flag: -D_GLIBCXX_DEBUG

I would only provide the flag for debug builds, but if debug is the default and release builds are a special target you should remove it:

release: CXXFLAGS := $(filter-out -D_GLIBCXX_DEBUG,$(CXXFLAGS)) -O2

This has fixed the same problem for me.

The last workaround mentioned in bug 24202 as linked by ks1322 is worth having a look at:

-fno-limit-debug-info will make your debug info larger, slow link (if you're not using -gsplit-dwarf) and debugger performance. But, yes, will address this.

Using -fno-limit-debug-info forces Clang to emit debug information for e.g. std::string at the cost of a larger binary while preserving compatibility with other libraries and the rest of the system/SDK.

As ks1322 and Kevin mentioned, one can instead use -D_GLIBCXX_DEBUG to switch libstdc++ into debug mode but this comes at a heavy price: any library you link against and with which you exchange STL containers (string, vector, etc.) must also be built with -D_GLIBCXX_DEBUG. Meaning: your system/SDK must either support this with a separate set of libraries or you will have to rebuild them yourself.

I've reproduced this issue on Fedora with system clang.

It appears that clang is not emitting debug information for std::string because it was told that libstdc++ provides it. See this comment from bug 24202:

Looks like you don't have debug information for libstdc++ installed:

Missing separate debuginfos, use: dnf debuginfo-install libgcc-5.1.1-4.fc22.x86_64 libstdc++-5.1.1-4.fc22.x86_64

Clang is not emitting debug information for std::string because it was told that libstdc++ provides it (but in your case, it's not installed); this is a debug size optimization that GCC apparently doesn't perform.

Does this work if you install the debug information for libstdc++?

I've installed debug info for libstdc++ with command dnf debuginfo-install libstdc++-6.2.1-2.fc25.x86_64 and that resolved the issue.