[gcc/devel/c++-modules] doc: Note that some warnings depend on optimizations (PR 92757)

[Nathan Sidwell]

https://gcc.gnu.org/g:aef85e40e0c5e242f1a1883abc56159dcd90e7b0

commit aef85e40e0c5e242f1a1883abc56159dcd90e7b0
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon Dec 2 21:32:54 2019 +0000

    doc: Note that some warnings depend on optimizations (PR 92757)
    
    	PR driver/92757
    	* doc/invoke.texi (Warning Options): Add caveat about some warnings
    	depending on optimization settings.

Diff:
---
 gcc/ChangeLog       | 6 ++++++
 gcc/doc/invoke.texi | 5 +++++
 2 files changed, 11 insertions(+)

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index f7df073..b2d12f4 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2020-01-13  Jonathan Wakely  <jwakely@redhat.com>
+
+	PR driver/92757
+	* doc/invoke.texi (Warning Options): Add caveat about some warnings
+	depending on optimization settings.
+
 2020-01-13  Jakub Jelinek  <jakub@redhat.com>
 
 	PR tree-optimization/90838
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index f2c805c..ab307b8 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -4575,6 +4575,11 @@ are being produced.  This allows the use of new @option{-Wno-} options
 with old compilers, but if something goes wrong, the compiler
 warns that an unrecognized option is present.
 
+The effectiveness of some warnings depends on optimizations also being
+enabled. For example @option{-Wsuggest-final-types} is more effective
+with link-time optimization and @option{-Wmaybe-uninitialized} will not
+warn at all unless optimization is enabled.
+
 @table @gcctabopt
 @item -Wpedantic
 @itemx -pedantic