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For big (legacy) code-bases, just upgrading the compiler is a project by itself. All 3rd party C++ libs need to be upgraded, all internal projects need to upgr

For big (legacy) code-bases, just upgrading the compiler is a project by itself. All 3rd party C++ libs need to be upgraded, all internal projects need to upgrade in an orderly fashion. On top of that, just the change of the compiler will expose some pre-existing bugs.The bugs might have been there, but are not a problem for the business if they currently don't show. I've seen projects with a core team of half a dozen people, supported by the other SW engineers working for 6 months just to upgrade to a newer version of windows and the compiler. This was mostly due to unwise SW-design decisions accumulated over 15+ years.

w-m 7y ago
I totally agree, updating compilers is painful, and can be hard even for smaller projects. But for projects that went through that and actually got the newer compiler working with the C++11 code, I haven't yet seen anything that breaks compilation when then switching the compiler flag to C++14 mode.
jandrewrogers 7y ago
You raise a good point about newer compilers doing much deeper analysis of the code than older compilers. I have experienced the horror of compiling an old, nominally clean C++11 code base with the latest version of clang++ and seeing a small avalanche of errors and warnings that weren't picked up by the compiler when that code was written. It creates a lot of work, and frequently the nature of the bugs are not material (i.e. in context they may not produce a runtime fault), but I do find it to be good hygiene. I used to do builds with two different compilers for the same purpose, though that found compiler bugs as often as it found issues in the code.
d1zzy 7y ago
Plus, a lot of new library and language features are simply standardized versions of features that mature codebases had their own solutions for years, so "upgrading" to a newer C++ may also imply a long process of deprecating these alternatives in favor of standard ones, and the subtle differences between the two can expose new bugs and issues.
cpeterso 7y ago
Here is a list of some real-world examples of bugs that Mozilla had to fix when upgrading from Firefox from C++11 to C++14 to C++17 (still in progress). Many of these are compiler issues from upgrading to clang or gcc versions recent enough to support the new C++ versions, not C++ language changes. https://bugzilla.mozilla.org/showdependencytree.cgi?id=1560664&hide_resolved=0 https://bugzilla.mozilla.org/showdependencytree.cgi?id=15606...
- dgellow 7y ago
  Your link requires to be logged in to see the actual bug ticket.
  - cpeterso 7y ago
    Oops. Sorry! Here is a different view of the bugs. I verified this list didn't require Bugzilla account. https://bugzilla.mozilla.org/buglist.cgi?bug_id=1396098%2C1390524%2C1377959%2C1526245%2C1395722%2C1396892%2C1238661%2C1390640%2C1238635%2C1577869%2C1194806%2C1401226%2C1577867%2C1411692%2C1378600%2C1584296%2C1379835%2C1579189%2C1412825%2C1172109%2C1278868%2C1560667%2C1335710%2C1577910%2C1322792%2C1369992%2C1507636%2C1578107%2C1416183%2C1577326%2C1580028%2C1577934%2C1262052%2C1246772%2C1377962%2C1396862%2C1413555%2C1573820%2C1378830%2C1396867%2C1278871%2C1278861%2C1577871%2C1029346%2C1396863%2C1412513%2C1278863%2C1396864%2C1243331%2C1396850%2C1536848%2C1029245%2C1412988%2C1277236%2C1581941%2C1569728%2C1378605%2C1577583%2C1029325%2C1412405%2C1411694%2C1577831%2C1576751%2C1593673%2C1410959%2C1396865%2C1577319%2C1399315%2C1163171%2C1578025%2C1411613%2C1288442%2C1412547%2C1396869%2C1578535%2C1412546%2C1577932%2C1577885%2C1578876%2C1412785%2C1377970%2C1396882%2C1412888%2C1577936%2C1277853%2C1277649%2C1277619%2C1325632%2C1412791%2C1577916%2C1282096%2C1577272%2C1414636%2C1195477%2C1578024%2C1277650%2C1414506%2C1377971%2C1396889%2C1277646%2C1577275%2C1560666%2C1577650%2C1278314%2C1433418%2C1573733%2C1412734%2C1370133%2C1320656%2C1277647%2C1379032%2C1593703%2C1577915%2C1277624&list_id=14976398 https://bugzilla.mozilla.org/buglist.cgi?bug_id=1396098%2C13...

w-m 7y ago

I totally agree, updating compilers is painful, and can be hard even for smaller projects. But for projects that went through that and actually got the newer compiler working with the C++11 code, I haven't yet seen anything that breaks compilation when then switching the compiler flag to C++14 mode.

jandrewrogers 7y ago

You raise a good point about newer compilers doing much deeper analysis of the code than older compilers. I have experienced the horror of compiling an old, nominally clean C++11 code base with the latest version of clang++ and seeing a small avalanche of errors and warnings that weren't picked up by the compiler when that code was written. It creates a lot of work, and frequently the nature of the bugs are not material (i.e. in context they may not produce a runtime fault), but I do find it to be good hygiene. I used to do builds with two different compilers for the same purpose, though that found compiler bugs as often as it found issues in the code.

d1zzy 7y ago

Plus, a lot of new library and language features are simply standardized versions of features that mature codebases had their own solutions for years, so "upgrading" to a newer C++ may also imply a long process of deprecating these alternatives in favor of standard ones, and the subtle differences between the two can expose new bugs and issues.

cpeterso 7y ago

Here is a list of some real-world examples of bugs that Mozilla had to fix when upgrading from Firefox from C++11 to C++14 to C++17 (still in progress). Many of these are compiler issues from upgrading to clang or gcc versions recent enough to support the new C++ versions, not C++ language changes. https://bugzilla.mozilla.org/showdependencytree.cgi?id=1560664&hide_resolved=0 https://bugzilla.mozilla.org/showdependencytree.cgi?id=15606...

dgellow 7y ago
Your link requires to be logged in to see the actual bug ticket.
- cpeterso 7y ago
  Oops. Sorry! Here is a different view of the bugs. I verified this list didn't require Bugzilla account. https://bugzilla.mozilla.org/buglist.cgi?bug_id=1396098%2C1390524%2C1377959%2C1526245%2C1395722%2C1396892%2C1238661%2C1390640%2C1238635%2C1577869%2C1194806%2C1401226%2C1577867%2C1411692%2C1378600%2C1584296%2C1379835%2C1579189%2C1412825%2C1172109%2C1278868%2C1560667%2C1335710%2C1577910%2C1322792%2C1369992%2C1507636%2C1578107%2C1416183%2C1577326%2C1580028%2C1577934%2C1262052%2C1246772%2C1377962%2C1396862%2C1413555%2C1573820%2C1378830%2C1396867%2C1278871%2C1278861%2C1577871%2C1029346%2C1396863%2C1412513%2C1278863%2C1396864%2C1243331%2C1396850%2C1536848%2C1029245%2C1412988%2C1277236%2C1581941%2C1569728%2C1378605%2C1577583%2C1029325%2C1412405%2C1411694%2C1577831%2C1576751%2C1593673%2C1410959%2C1396865%2C1577319%2C1399315%2C1163171%2C1578025%2C1411613%2C1288442%2C1412547%2C1396869%2C1578535%2C1412546%2C1577932%2C1577885%2C1578876%2C1412785%2C1377970%2C1396882%2C1412888%2C1577936%2C1277853%2C1277649%2C1277619%2C1325632%2C1412791%2C1577916%2C1282096%2C1577272%2C1414636%2C1195477%2C1578024%2C1277650%2C1414506%2C1377971%2C1396889%2C1277646%2C1577275%2C1560666%2C1577650%2C1278314%2C1433418%2C1573733%2C1412734%2C1370133%2C1320656%2C1277647%2C1379032%2C1593703%2C1577915%2C1277624&list_id=14976398 https://bugzilla.mozilla.org/buglist.cgi?bug_id=1396098%2C13...