[clang] [clang][analyzer] Change default value of checker option in unix.StdCLibraryFunctions. (PR #80457)

[Balázs Kéri via cfe-commits]

balazske wrote:

The change was evaluated on the following projects. "Lost reports" shows results that disappear if the `ModelPOSIX` option is changed to true. "New reports" shows the new results. Many of the new results come from the large number of modeled functions. The lost reports are more interesting (some are at project postgres), probably the analysis changes because preconditions of functions are applied (if the option is turned on).

| Project | Lost Reports | New Reports |
|---------|-------------|--------------|
| memcached | [new reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=memcached_1.6.8_modelposix_defaulton&newcheck=memcached_1.6.8_modelposix_defaultoff&is-unique=on&diff-mode=New) | [lost reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=memcached_1.6.8_modelposix_defaulton&newcheck=memcached_1.6.8_modelposix_defaultoff&is-unique=on&diff-mode=Resolved) |
| tmux | [new reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=tmux_2.6_modelposix_defaulton&newcheck=tmux_2.6_modelposix_defaultoff&is-unique=on&diff-mode=New) | [lost reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=tmux_2.6_modelposix_defaulton&newcheck=tmux_2.6_modelposix_defaultoff&is-unique=on&diff-mode=Resolved) |
| curl | [new reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=curl_curl-7_66_0_modelposix_defaulton&newcheck=curl_curl-7_66_0_modelposix_defaultoff&is-unique=on&diff-mode=New) | [lost reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=curl_curl-7_66_0_modelposix_defaulton&newcheck=curl_curl-7_66_0_modelposix_defaultoff&is-unique=on&diff-mode=Resolved) |
| twin | [new reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=twin_v0.8.1_modelposix_defaulton&newcheck=twin_v0.8.1_modelposix_defaultoff&is-unique=on&diff-mode=New) | [lost reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=twin_v0.8.1_modelposix_defaulton&newcheck=twin_v0.8.1_modelposix_defaultoff&is-unique=on&diff-mode=Resolved) |
| vim | [new reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=vim_v8.2.1920_modelposix_defaulton&newcheck=vim_v8.2.1920_modelposix_defaultoff&is-unique=on&diff-mode=New) | [lost reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=vim_v8.2.1920_modelposix_defaulton&newcheck=vim_v8.2.1920_modelposix_defaultoff&is-unique=on&diff-mode=Resolved) |
| openssl | [new reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=openssl_openssl-3.0.0-alpha7_modelposix_defaulton&newcheck=openssl_openssl-3.0.0-alpha7_modelposix_defaultoff&is-unique=on&diff-mode=New) | [lost reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=openssl_openssl-3.0.0-alpha7_modelposix_defaulton&newcheck=openssl_openssl-3.0.0-alpha7_modelposix_defaultoff&is-unique=on&diff-mode=Resolved) |
| sqlite | [new reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=sqlite_version-3.33.0_modelposix_defaulton&newcheck=sqlite_version-3.33.0_modelposix_defaultoff&is-unique=on&diff-mode=New) | [lost reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=sqlite_version-3.33.0_modelposix_defaulton&newcheck=sqlite_version-3.33.0_modelposix_defaultoff&is-unique=on&diff-mode=Resolved) |
| ffmpeg | [new reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=ffmpeg_n4.3.1_modelposix_defaulton&newcheck=ffmpeg_n4.3.1_modelposix_defaultoff&is-unique=on&diff-mode=New) | [lost reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=ffmpeg_n4.3.1_modelposix_defaulton&newcheck=ffmpeg_n4.3.1_modelposix_defaultoff&is-unique=on&diff-mode=Resolved) |
| postgres | [new reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=postgres_REL_13_0_modelposix_defaulton&newcheck=postgres_REL_13_0_modelposix_defaultoff&is-unique=on&diff-mode=New) | [lost reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=postgres_REL_13_0_modelposix_defaulton&newcheck=postgres_REL_13_0_modelposix_defaultoff&is-unique=on&diff-mode=Resolved) |
| xerces | [new reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=xerces_v3.2.3_modelposix_defaulton&newcheck=xerces_v3.2.3_modelposix_defaultoff&is-unique=on&diff-mode=New) | [lost reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=xerces_v3.2.3_modelposix_defaulton&newcheck=xerces_v3.2.3_modelposix_defaultoff&is-unique=on&diff-mode=Resolved) |
| bitcoin | [new reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=bitcoin_v0.20.1_modelposix_defaulton&newcheck=bitcoin_v0.20.1_modelposix_defaultoff&is-unique=on&diff-mode=New) | [lost reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=bitcoin_v0.20.1_modelposix_defaulton&newcheck=bitcoin_v0.20.1_modelposix_defaultoff&is-unique=on&diff-mode=Resolved) |


https://github.com/llvm/llvm-project/pull/80457