https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83441
Bug ID: 83441 Summary: Null this captured in lambda in class variable initializer for templated classes Product: gcc Version: 7.2.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: alextenbrink at gmail dot com Target Milestone: --- Created attachment 42896 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=42896&action=edit Preprocessed compilation result on example The following code prints '0', signifying that the capture 'this' pointer is null: #include<iostream> #include<functional> template<bool Dummy> struct X { std::function<void()> f{[this]{ std::cout << (void*)this << "\n"; }}; }; int main() { X<true> x; x.f(); return 0; } Removing the template parameter of the class, or moving the initializer to a constructor makes the program print a nonzero value, for example: #include<iostream> #include<functional> template<bool Dummy> struct X { X() : f{[this]{ std::cout << (void*) this << "\n"; }}{} std::function<void()> f; }; int main() { X<true> x; x.f(); return 0; } My expected behaviour is that the 'this' pointer is not null. It looks like this problem repos in previous versions of GCC - if I try this code in an online compiler, I even get internal compiler errors on some sites. Version and command information (I'm using a locally compiled gcc 7.2): /usr/local/bin/g++ -v -save-temps -Wall -Wextra -fno-strict-aliasing -fwrapv -fno-aggressive-loop-optimizations -fsanitize=undefined bug.cpp && ./a.out Using built-in specs. COLLECT_GCC=/usr/local/bin/g++ COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc/x86_64-pc-linux-gnu/7.2.0/lto-wrapper Target: x86_64-pc-linux-gnu Configured with: ../gcc-7.2.0/configure --enable-languages=c++ --disable-multilib Thread model: posix gcc version 7.2.0 (GCC) COLLECT_GCC_OPTIONS='-v' '-save-temps' '-Wall' '-Wextra' '-fno-strict-aliasing' '-fwrapv' '-fno-aggressive-loop-optimizations' '-fsanitize=undefined' '-shared-libgcc' '-mtune=generic' '-march=x86-64' /usr/local/libexec/gcc/x86_64-pc-linux-gnu/7.2.0/cc1plus -E -quiet -v -imultiarch x86_64-linux-gnu -D_GNU_SOURCE bug.cpp -mtune=generic -march=x86-64 -Wall -Wextra -fno-strict-aliasing -fwrapv -fno-aggressive-loop-optimizations -fsanitize=undefined -fpch-preprocess -o bug.ii COLLECT_GCC_OPTIONS='-v' '-save-temps' '-Wall' '-Wextra' '-fno-strict-aliasing' '-fwrapv' '-fno-aggressive-loop-optimizations' '-fsanitize=undefined' '-shared-libgcc' '-mtune=generic' '-march=x86-64' /usr/local/libexec/gcc/x86_64-pc-linux-gnu/7.2.0/cc1plus -fpreprocessed bug.ii -quiet -dumpbase bug.cpp -mtune=generic -march=x86-64 -auxbase bug -Wall -Wextra -version -fno-strict-aliasing -fwrapv -fno-aggressive-loop-optimizations -fsanitize=undefined -o bug.s GNU C++14 (GCC) version 7.2.0 (x86_64-pc-linux-gnu) compiled by GNU C version 7.2.0, GMP version 6.1.0, MPFR version 3.1.4, MPC version 1.0.3, isl version none GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072 GNU C++14 (GCC) version 7.2.0 (x86_64-pc-linux-gnu) compiled by GNU C version 7.2.0, GMP version 6.1.0, MPFR version 3.1.4, MPC version 1.0.3, isl version none GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072 Compiler executable checksum: c1b49aafb451e1f859453c52dc4e5f71 COLLECT_GCC_OPTIONS='-v' '-save-temps' '-Wall' '-Wextra' '-fno-strict-aliasing' '-fwrapv' '-fno-aggressive-loop-optimizations' '-fsanitize=undefined' '-shared-libgcc' '-mtune=generic' '-march=x86-64' as -v --64 -o bug.o bug.s GNU assembler version 2.26.1 (x86_64-linux-gnu) using BFD version (GNU Binutils for Ubuntu) 2.26.1 COMPILER_PATH=/usr/local/libexec/gcc/x86_64-pc-linux-gnu/7.2.0/:/usr/local/libexec/gcc/x86_64-pc-linux-gnu/7.2.0/:/usr/local/libexec/gcc/x86_64-pc-linux-gnu/:/usr/local/lib/gcc/x86_64-pc-linux-gnu/7.2.0/:/usr/local/lib/gcc/x86_64-pc-linux-gnu/ LIBRARY_PATH=/usr/local/lib/gcc/x86_64-pc-linux-gnu/7.2.0/:/usr/local/lib/gcc/x86_64-pc-linux-gnu/7.2.0/../../../../lib64/:/lib/x86_64-linux-gnu/:/lib/../lib64/:/usr/lib/x86_64-linux-gnu/:/usr/local/lib/gcc/x86_64-pc-linux-gnu/7.2.0/../../../:/lib/:/usr/lib/ COLLECT_GCC_OPTIONS='-v' '-save-temps' '-Wall' '-Wextra' '-fno-strict-aliasing' '-fwrapv' '-fno-aggressive-loop-optimizations' '-fsanitize=undefined' '-shared-libgcc' '-mtune=generic' '-march=x86-64' /usr/local/libexec/gcc/x86_64-pc-linux-gnu/7.2.0/collect2 -plugin /usr/local/libexec/gcc/x86_64-pc-linux-gnu/7.2.0/liblto_plugin.so -plugin-opt=/usr/local/libexec/gcc/x86_64-pc-linux-gnu/7.2.0/lto-wrapper -plugin-opt=-fresolution=bug.res -plugin-opt=-pass-through=-lgcc_s -plugin-opt=-pass-through=-lgcc -plugin-opt=-pass-through=-lc -plugin-opt=-pass-through=-lgcc_s -plugin-opt=-pass-through=-lgcc --eh-frame-hdr -m elf_x86_64 -dynamic-linker /lib64/ld-linux-x86-64.so.2 /usr/lib/x86_64-linux-gnu/crt1.o /usr/lib/x86_64-linux-gnu/crti.o /usr/local/lib/gcc/x86_64-pc-linux-gnu/7.2.0/crtbegin.o -L/usr/local/lib/gcc/x86_64-pc-linux-gnu/7.2.0 -L/usr/local/lib/gcc/x86_64-pc-linux-gnu/7.2.0/../../../../lib64 -L/lib/x86_64-linux-gnu -L/lib/../lib64 -L/usr/lib/x86_64-linux-gnu -L/usr/local/lib/gcc/x86_64-pc-linux-gnu/7.2.0/../../.. bug.o -lstdc++ -lm -lubsan -lgcc_s -lgcc -lc -lgcc_s -lgcc /usr/local/lib/gcc/x86_64-pc-linux-gnu/7.2.0/crtend.o /usr/lib/x86_64-linux-gnu/crtn.o COLLECT_GCC_OPTIONS='-v' '-save-temps' '-Wall' '-Wextra' '-fno-strict-aliasing' '-fwrapv' '-fno-aggressive-loop-optimizations' '-fsanitize=undefined' '-shared-libgcc' '-mtune=generic' '-march=x86-64' 0