wwbQzhMkhhgEmhU score 237
2019/02/13 18:47 投稿
| > このように初期化した場合最初の３つがpositionにはいってあとの３つがnormalに入るんですか？ |
| はい。 |
| > あと{ 1.0f, -1.0f, -1.0f)のように３つだけ書いたらどうなりますか？ |
| 後半3つは既定の値(GLfloat知らないけど多分0)が入ります。 |
| 規格に近いものは、普通に落ちてるのだと、 |
| https://cpprefjp.github.io/lang/cpp11/initializer_lists.html |
| 処理系のマニュアルだと |
| (Visual C++) |
| https://docs.microsoft.com/ja-jp/cpp/cpp/initializers?view=vs-2017 |
| gccで試した結果だと |
| ```C++ |
| struct Vertex |
| { |
| float position[3]; |
| float normal[3]; |
| }; |
| Vertex a[] = { |
| {{1,2,3},{4,5,6}}, // 普通 |
| {{2,3},{5,6}}, // 少ない |
| //{{2,3,4},{5,6,7 |
| //{{2,3,4},{5,6,7,8}}, 多い。これはgcc 8.2.0だとエラー |
| {2,3,4,5,6,7}, // 古い書き方(普通) |
| {2,3,4,5,6}, // 古い書き方(少ない) |
| //{2,3,4,5,6,7,8} 古い書き方(多い)。これはgcc 8.2.0だとエラー |
| }; |
| ``` |
| ```text |
| user@lubuntu:~/cpp$ cat test.cpp |
| struct Vertex |
| { |
| float position[3]; |
| float normal[3]; |
| }; |
| Vertex a[] = { |
| {{1,2,3},{4,5,6}}, // 普通 |
| {{2,3},{5,6}}, // 少ない |
| //{{2,3,4},{5,6,7}}, 多い。これはgcc 8.2.0だとエラー |
| {2,3,4,5,6,7}, // 古い書き方(普通) |
| {2,3,4,5,6}, // 古い書き方(少ない) |
| //{2,3,4,5,6,7,8} 古い書き方(多い)。これはgcc 8.2.0だとエラー |
| }; |
| int main() {return 0;} |
| user@lubuntu:~/cpp$ g++ -g test.cpp -o test |
| user@lubuntu:~/cpp$ gdb test |
| GNU gdb (Ubuntu 8.2-0ubuntu1) 8.2 |
| Copyright (C) 2018 Free Software Foundation, Inc. |
| License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> |
| This is free software: you are free to change and redistribute it. |
| There is NO WARRANTY, to the extent permitted by law. |
| Type "show copying" and "show warranty" for details. |
| This GDB was configured as "x86_64-linux-gnu". |
| Type "show configuration" for configuration details. |
| For bug reporting instructions, please see: |
| <http://www.gnu.org/software/gdb/bugs/>. |
| Find the GDB manual and other documentation resources online at: |
| <http://www.gnu.org/software/gdb/documentation/>. |
| For help, type "help". |
| Type "apropos word" to search for commands related to "word"... |
| Reading symbols from test...done. |
| (gdb) break main |
| Breakpoint 1 at 0x1129: file test.cpp, line 16. |
| (gdb) run |
| Starting program: /home/user/cpp/test |
| Breakpoint 1, main () at test.cpp:16 |
| 16 int main() {return 0;} |
| (gdb) display a |
| 1: a = {{position = {1, 2, 3}, normal = {4, 5, 6}}, {position = {2, 3, 0}, normal = {5, 6, 0}}, { |
| position = {2, 3, 4}, normal = {5, 6, 7}}, {position = {2, 3, 4}, normal = {5, 6, 0}}} |
| (gdb) |
| ``` |
| 多くてエラーになるケース(1) |
| ```text |
| user@lubuntu:~/cpp$ cat test.cpp |
| struct Vertex |
| { |
| float position[3]; |
| float normal[3]; |
| }; |
| Vertex a[] = { |
| {{1,2,3},{4,5,6}}, // 普通 |
| {{2,3},{5,6}}, // 少ない |
| {{2,3,4},{5,6,7,8}},// 多い。これはgcc 8.2.0だとエラー |
| {2,3,4,5,6,7}, // 古い書き方(普通) |
| {2,3,4,5,6}, // 古い書き方(少ない) |
| //{2,3,4,5,6,7,8} // 古い書き方(多い)。これはgcc 8.2.0だとエラー |
| }; |
| int main() {return 0;} |
| user@lubuntu:~/cpp$ g++ -g test.cpp -o test |
| test.cpp:14:1: error: too many initializers for ‘float [3]’ |
| }; |
| ^ |
| user@lubuntu:~/cpp$ |
| ``` |
| 多くてエラーになるケース(2) |
| ```text |
| user@lubuntu:~/cpp$ cat test.cpp |
| struct Vertex |
| { |
| float position[3]; |
| float normal[3]; |
| }; |
| Vertex a[] = { |
| {{1,2,3},{4,5,6}}, // 普通 |
| {{2,3},{5,6}}, // 少ない |
| //{{2,3,4},{5,6,7,8}}, 多い。これはgcc 8.2.0だとエラー |
| {2,3,4,5,6,7}, // 古い書き方(普通) |
| {2,3,4,5,6}, // 古い書き方(少ない) |
| {2,3,4,5,6,7,8} // 古い書き方(多い)。これはgcc 8.2.0だとエラー |
| }; |
| int main() {return 0;} |
| user@lubuntu:~/cpp$ g++ -g test.cpp -o test |
| test.cpp:14:1: error: too many initializers for ‘Vertex’ |
| }; |
| ^ |
| user@lubuntu:~/cpp$ |
| ``` |
